HomeMy WebLinkAboutBradley Lake Final Supporting Design Report Vol 2 Design Criteria 1986Alaska Power Authority
FINAL SUPPORTING DESIGN REPORT
SITE PREPARATION CONTRACT
BRADLEY LAKE
HYDROELECTRIC PROJECT
FEDERAL ENERGY REGULATORY COMMISSION
PROJECT NO. P-8221-000
VOWME 2
DESIGN CRITERIA
Prepared By
STONE & WEBSTER ENGINEERING CORPORATION
ANCHORAGE , ALASKA
March , 1986
Alaska -Power Authority
FINAL SUPPORTING DESIGN REPORT
SITE PREPARATION CONTRACT
BRADLEY LAKE
HYDROELECTRIC PROJECT
FEDERAL ENERGY REGULATORY COMMISSION
PROJECT NO. P-8221-000
VOLUME 2
DESIGN CRITERIA
Prepared By
STONE & WEBSTER ENGINEERING CORPORATION
ANCHORAGE. ALASKA
March. 1986
TABLE OF CONTENTS
TABLE OF CONTENTS
FINAL SUPPORTING DESIGN REPORT
SITE PREPARATION CONTRACT
VOLUME l
REPORT
1.0 INTRODUCTION
2.0 DESIGN AND GENERAL TECHNICAL DATA
2.1 DESIGN
2.2 DESIGN LOADS
2.3 STABILITY CRITERIA
3.0 SUITABILITY ASSESSMENT
3.1 SPECIFIC ASSESSMENTS
3.2 EXECUTIVE SUMMARY OF FINAL SITE CONDITIONS REPORT
4.0 BORINGS, GEOLOGICAL REPORTS, AND LABORATORY TEST
REPORTS
5.0 BORROW AREAS AND QUARRY SITES
5.1 BORROW AREA LOCATION
5.2 BORROW QUANTITIES
5.3 QUARRY SITES
6.0 STABILITY AND STRESS ANALYSIS
6.1 GENERAL
6.2 DIVERSION TUNNEL INCLUDING INTAKE
6.3 DOWNSTREAM CHANNEL IMPROVEMENT
6.4 MAIN DAM
6. 5 SPILLWAY
6.6 MIDDLE FORK DIVERSION DAM
6.7 POWERHOUSE
6.8 REFERENCES
7.0 BASIS FOR SEISMIC LOADING
7.1 GENERAL
7.2 SEISMOTECTONIC SETTING
7.3 SEISMIC DESIGN
8.0 SPILLWAY DESIGN FLOOD BASIS
8.1 STUDY METHODOLOGY
8.2 MODEL CALIBRATION
8.3 PROBABLE MAXIMUM FLOODS
8.4 STANDARD PROJECT FLOOD
8.5 SPILLWAY DESIGN FLOOD
2-379-JJ
i
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
SITE PREPARATION CONTRACT
VOLUME 1
REPORT
9.0 BOARD OF CONSULTANTS
9.1 INDEPENDENT BOARD OF CONSULTANTS
9.3 FERC BOARD OF CONSULTANTS
ii
2-379-JJ
APPENDIX A
Plate
Exhibit F
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Figures
F.6.2-5
F.6.2-6
2-379-JJ
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
SITE PREPARATION CONTRACT
VOLUME 1
REPORT
DRAWINGS
Title
General Plan
General Arrangement -Dam, Spillway and Flow Structures
Concrete Faced Rockfill Dam -Sections and Details
Spillway -Plan, Elevations and Sections
Power Conduit Profile and Details
Intake Channel and Power Tunnel Gate Shaft -Sections and
Details
Site Preparation Excavation at Powerhouse -Plan
Site Preparation Excavation at Powerhouse -Elevations
90 MW Pelton Powerhouse -Elevation
Construction Diversion -Sections and Details
Middle Fork Diversion -Plan and Profile
Middle Fork Diversion -Elevation and Details
Main Dam Diversion -Channel Improvements
General Arrangement -Permanent Camp and Powerhouse
Barge Dock
Powerhouse Substation and Bradley Junction
Main One. Line Diagram
Martin River Borrow Area
Waterfowl Nesting Area
Mean Horizontal Response Spectrum
Design Accelerogram
iii
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
SITE PREPARATION CONTRACT
VOLUME 1
REPORT
APPENDIX B LIST OF ATTACHMENTS
B.1 Construction Schedule Contract Dates
B.2 Independent Board of Consultant's Meetings:
Meeting No. 1 May 12 and 13, 1983
Meeting No. 2 July 11 to 15, 1983
Meeting No. 3 September 25 to 27, 1984
Meeting No. 4 November 4 and 5, 1985
Meeting No. 5 January 28, 1986
B.3 FERC Board of Consultant's Meeting:
Meeting No. 1 March 6 and 7, 1986
APPENDIX C
The Final Site Conditions Report of Geotechnical Field
Investigation for Bradley Lake Hydroelectric Project - 1984 and
1985 Programs is included with this report.
iv
2-379-JJ
.·. ·'·
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
SITE PREPARATION CONTRACT
VOLUME 2
DESIGN CRITERIA
1.0 Design Criteria for Civil Structures:
1.2 Permanent Access Road
1.3 Permanent Bridges
1.4 Borrow Areas
1. 5 Barge Dock
1. 6 Airstrip
1.7 Temporary and Permanent Camps
2.0 Geotechnical Design Criteria -Site Preparation
3.0 Structural Design Criteria -Main Dam Diversion
4.0 Hydraulic Design Criteria -Main Dam Diversion
v
2-379-JJ
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
SITE PREPARATION CONTRACT
VOLUME 3
CALCULATIONS
Title
GEOTECHNICAL
1.
2.
3.
4.
5.
6.
7.
8.
9.
HYDRAULIC
1.
2.
3.
2-379-JJ
Main Dam Diversion
Tunnel Alignment and Surface Excavation
Stability of Diversion Tunnel Portals
Design of Rock Reinforcement
Support System for Main Dam Diversion
Tunnel
Gabion Stability
Diversion Channel
Alignment and Excavation
Stability of Temporary Rock
Plug for Main Dam Diversion Tunnel
Powerhouse Benching Plan and Surface
Excavation
COE/BLHP Survey Datum
Correlation -Damsite
Rock Engineering/Design Criteria
Parameters
Design Channel Size Downstream of
Diversion Tunnel
Quantities of Excavation and Comparison
of Quantities for Various Depth of Channel
Quantities of Cofferdams
vi
Calculation
No.
G(A)-03
G(A)-07
G(A)-09
G(A)-14
G(A)-15
G(A)-17
G(A)-18
G(H)-19
G(A)-21
H-003
H-004
H-008
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
SITE PREPARATION CONTRACT
VOLUME 4
CALCULATIONS
Title
HYDRAULIC (Continued)
4.
s.
6.
7.
8.
9.
Water Surface Profile in Diversion Tunnel
Fish By-Pass Pipe System
Forcing Frequency for Diversion Intake Pier
Lake Drawdown
Design of Channel Downstream of Diversion
Tunnel
Water Surface Profiles Downstream of
Diversion Tunnel
10. Bulkhead Gate Operation
Diversion Tunnel
11. Water Surface Profile Diversion Tunnel
12. Riprap Design -Bank Across Pool from
Diversion Tunnel
13. Relationship of USGS Gaging Stations to
Bradley Lake Project Datum
14. Synthesize Flood of Record Inflow
Hydrograph from Recorded Outflow Hydrograph
at Bradley Lake
15. Flood Routing Flood of Record through
Bradley Lake and Diversion Tunnel
vii
2-379-JJ
Calculation
No.
H-010
H-012
H-014
H-015
H-016
H-017
H-018
H-019
H-021
H-024
H-029
H-033
STRUCTURAL
1.
2.
3.
4.
2-379-JJ
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
SITE PREPARATION CONTRACT
VOLUME 4
CALCULATIONS
Title
Wind Loads for Design Criteria
Snow and Ice Loads for Design Criteria
Main Dam Diversion -Intake Portal
Analysis and Design
Main Dam Diversion -Intake Bulkheads
viii
Calculation
No.
SDC-1
SDC-2
SC-131-1
SS-132-2
DESIGN CRITERIA FOR
CIVIL STRUCTURES
8/7 1
BRADLEY LAKE HYDRO PROJECT
CIVIL WORKS DESIGN CRITERIA
Revised January 13, 1986
RECOMMENDED ACCESS ROAD CRITERIA
The access roads are divided into four basic segments according to
function and similarities of construction of follows:
Item
Road Type
Design Speed (mph)
0
0
0
0
Lane Width (travel surf.)
Shoulders
Horizontal Curves =
Sight Distance
Airport to powerhouse
Powerhouse to lower camp
Lower camp to dam
Martin River borrow access road
Criteria
Resource Development Road. Two-lane in higher
traffic areas such as powerhouse to lower camp
segment. Single lane between lower camp and
dam, powerhouse to airstrip, and Martin River
borrow access.
Single Lane*
20
12'
2'
100' min R
300'
Single Lane**
20
14'
2'
100' min R
300'
Two-lane
20
12'
2'
100' min R
150'
* Single fane road from lower camp to dam.
**Single lane road to Martin River borrow site and powerhouse to airstrip-
Vertical Curvature
Maximum Grades
Super-elevation
Crown Cross Slope
Clearing
Stripping
Surfacing
Culverts
To be calculated in accordance with State of
Alaska DOTPF Highway Preconstruction
Manual procedure 11-10-5. Value dependent
on design speed and grade difference.
Desirable 10%, Maximum 14%
Not to exceed 4%.
0. 03-foot per foot.
10' from edge of cut slope or 10' from toe of
fill, or as necessary for sight distance.
5' from edge of cut slope or 10' from toe of
fill
2" minus gravel, 6" thick
24" Min. CMP, 16 gage minimum, inlet
armored and flared.
•
•
8/7 2
Road Elevation 0.5 feet above 50 year frequency waves 1n
tidal areas
0.5 feet above 50 year flood level of Battle
Creek
The following four items apply only to the one-way roads:
Ditch Widening
Curve Widening
Fill Widening
Turnouts
Ditches on cut side to be widened 4' in rock
cuts 20 feet or over in height.
Inside of curves to be widened from 4 feet
on a 100 foot radius to 2 feet on a 200 foot
radius curve.
Selected fills will be widened with excess cut
materials when available.
Maximum spacing 2600 feet; minimum spacing
500 feet.
150 feet long, 14 feet wide with 50 feet taper
at each end .
O'MII:
CKD:
/ ..:_U
18'
4'' / I
I-,--CUT SLOPE DEPENDENT I ON MATERIAL I 1~2 : I ::~:
<t.
I
RIPRAP IN TIDAL
AREAS SUBJECT " ,_ 6" GRAVEL SURFACE
-UNCLASSIFIED FILL
FROM EXCAVATION
AIRSTRIP TO POWERHOUSE
AIRSTRIP TO STA. 495 +00
28'
3o/o-
/
SURFACE___,/
I I_..,
~ '-BORROW EMBANKMENT
POWERHOUSE TO LOWER CAMP
STA. 495 +00 TO STA. 625 + 00
16'
5' I
MIN. ROAD ELEV. AND RIPRAP
ARMOR DESIGN BASED ON 50 YR
DESIGN WAVE WITH 0.5 FT FREESOAR£
I
I
LCUT SLOPE DEPENDENT
/1 ON MATERIAL
/ I
. I 1/2 ROCK
2 : I SOIL
CURVE WIDENING ON INSIDE
OF R200' CURVES OR LESS'·
:~ / FABRIC OR SUBORAIN
l I I I WHERE REQUIRED
·~ if ADO 4' FLAT BOTTOM
"
. \ / -:..::..:· ;:-:m.si.i' r:~'~m;;;~~~:.'i:l~ 0~'-:r;· m:!iii:..:J..4i.J· ~~ I, . / o 1 T c H wHERE HE 1 GHT
/ 1 \ -~--/ OF CUT IS 20' OR MOR::
·-)'/ --.---! "'--. • ... ;· . --Ji-.-,; ··--6"GRAVEL::OURFACE
/ ·,, ~~..:...~ "
· . ·• ----'---uNCLASSIFIED FILL
"ROM EXCAVATIO~J
LO\'/ER CAMP TO DAM
STA. 625 + 00 TO STA. 922 +00
REVISED II-1-85
REVISE 0 1-31-85
0 E P r~., s::::!--;'\t I
I ~~\/L-------------.. FB:
GRID: v J G ! ~!!~. '-=-~~.~~L.T~!;I~T~:~~~~~
DATE : JuLy 198 5 i II
SCALE; lit= 10 1
I ~================~
ACCESS ROAD
TYPICAL SECTIONS PROJ.NO: 551095
OWG.NO: I
•
I
11)
~· ------------------------------------\
DM-1: OEP
CKO: VJG
DATE: JULY 1985
SCAL.E:: I":: 10'
'!. ·. \
MARTIN RIVER ACCESS
I . 18' ·j
I li.
I I I 1_3% 3°/o-
I ~,""'" I
UIREO ,/1
BORROW FIL.L. I
I
I
I
,ti;<:;:->'I,I0Y/~ I /l~,t::-··o;:.""/1
FILL SECTION
MARTIN RIVER
ACCESS ROAD
TYPICAL SECTION
'/' ··>rf\'Y/-
FB:
GR!O:
PROJ NO : 55 I 0 9 5
OWC.NO: 2
I
I
l
I
• Tl* ~ ~ ~ ~ r ,.., rrJ •.
. ~I<IO ·r <-rra ~l~ m -o
0 1.0 -m
Ul
;-:Dl -:1
i 01 J I J J ; ~ r~~n , n L:~ ;o c~-:
gz
•Ill ;c
;£i
'1> i :2 ....
• !.1 i. ,-!2 ~n .. '-·-----'----~·--·--·'
_.
-<
"'0 -0 >
l> -
r :g
en
(}) _.
m ::0
0 -_. "'0 -0 z
0 ~~~~~ ~ <.. D z
0 0 ..
Ul
Ul
0
lb
01
-• -------------·· -··--··--------
RUNWAY SAFETY AREA . . ..
60'
RUtJWAY WIDTH
TOP EL.EV. o.!'AaOVE l r-----t ______ eo':: ...
50 YR WAVE +
_ .---_ _ _ -~ !!o__ _ !j'o --"'-----..__._. _ _.............. .. ·-·~-7-.-.. -=--------...,-F-.. 4'\_.--~ ~--~~~---·-···-~
'"'" ·;~_;~. /--~;~~S;l§-M~!}f.":~{t~.~~Il~E:ts, '
PIIASE II CONST. _-
TUilNEL CUTTING$ ...--
TYPICAL RUNWAY
CROSS SECTION
RUNWAY LENGTH 2200 FT.
/
8/7 4
HAULROAD TEMPORARY BRIDGES -DESIGN CRITERIA
System: Contractor to design
Design Life: 10 year life
Design Vehicle: HS25
Components:
Steel -50 ksi yield meeting minimum charpy requirements of AASHTO
Concrete -strength as dictated by design, 3000 psi min., 4000 psi at
water
Connections -welds as per AWS specification
-structural bolts ASTM A325
Foundations -as dictated by geotechnical evaulation, recommend
treated crib type foundations
Governing Codes: AASHTO -American Association of State Highway and
Transportation Officals.
)
8/7 5
AGGREGATE AND CONCRETE SUPPLY
ELEMENTS CONSIDERED ESSENTIAL OR DESIREABLE
1. Floodplain protection dike at Martin River site to be based on a 100
year flood of the Martin River.
2. Aggregate for road surfacing to be produced and placed under the
site preparation contract, plus a stockpile located in quarry area for
maintenance.
3. Riprap for revetment armor on roads and airstrip to be produced and
placed under the site preparation contract; plus a stockpile located in
quarry area for maintenance.
4. Concrete aggregate to be produced and stockpiled in the construction
camp area for use in the Phase II contract; quantities based on
design requirements for Phase II contract.
(~~~
\~
8/7 6
BARGE FACILITY RECOMMENDED DESIGN CRITERIA
DOCK
System: Sheet pile cell system with gravel embankment
Design Life: 5 years, 50 years with damage during major seismic events.
Design Loads: Uniform Load 500 psf
Crane Load -65K pad force from 150 ton crane (with 10% impact)
Fork Lift Load -62 ton axle load (with 30°& impact)
Barge Berthing and Breasting Forces -to be determined
Truck Loading HS25
Loader Load -80 ton axle (without impact) from Cat. 988
Components:
Steel sheet piles
corrosion protection.
ASTM A328 with coal tar epoxy and anode
Walers -ASTM A36, 36 ksi yield, coal tar epoxy coated
Tie-back rods -ASTM A36, 36 ksi yield, coal tar epoxy coated
Deadman -concrete, f' c = 3000 psi
Fenders -minimum, as necessary due to exposure condition and to
prevent barges from catching on walers
Governing Codes: AASHTO or U BC as applicable
•
8/7 7
Water Depth:
Outward loading face sited at 6 to -7 foot elevation Project Datum.
Access criteria developed will allow access by barges of 6 feet draft
during a period 2 hours before and after higher high water for a·
period of 12 to 15 days per month. Barges of greater draft can
access the site with careful planning to intercept the highest monthly
tides. Another ramped loading face shall be provided at -3± foot
elevation project datum to allow a more efficient end unloading
operation. A sloped ramp will also be provided for beaching smaller
barges and boats.
Staging Area:
The barge access facility shall have sufficient staging area (1 acre±),
for temporary storage of freight. No covered or secured staging
shall be provided.
BARGE BASIN AND ACCESS CHANNEL
Not Required.
DREDGE DISPOSAL AREA DESIGN
Only minimal dredging to be performed. This dredging (or
excavation) will likely be performed with a backhoe or track mounted
excavating equipment therefore settling _ponds. {etc. t should not be
required.
8/7 8
RECOMMENDED AIRPORT RUNWAY CRITERIA
The airport runway IS designed tn accordance with Federal Aviation
Administration specifications for basic utility stage I airports.
This airport is planned to have a landing area 2,680 feet long by 120 feet
wide. The airport will also include a parking apron with parking for two
resident airplanes, two transient airplanes, one heticopter, and temporary
shelter/storage shed such as a surplus container. An 18 foot wide access
road will be built from the airport to the powerhouse. The airport and
facilities will be constructed on a tidal flat near the powerhouse to a
height designed to prevent overtopping by storm waves from Kachemak
Bay. The bay side will be protected with rip rap. It is planned that this
airport will be built in two stages: The first stage will be built to
provide a minimum width embankment and is intended to provide a
servicable airport for the contractor to use during the initial stages of
construction. As material from the power tunnel excavation becomes
available, the airport and facilities will be constructed to full design
width.
Following is specific criteria developed to date for construction of the
airport.
Item
Runway Length
Runway Width
Criteria
2200 feet (Determined from FAA
advisory circular Figure 4-1. Based
on airport elevation and mean daily
maximum temperature for· hottest
month of year. )
60 feet
8/7 9
Item
Runway Safety Area
Length
Width
Building Restriction Line
Clear Zone
Width 0
Length 1
Width 1
Length 2
Width 2
Slope
Transition Slope
Runway Orientation
Location
Azimuth
Criteria
240 feet beyond each end of runway
30 feet beyond each side of runway
125 feet from centerline
Begins 200 feet beyond end of runway
250 feet
1000 feet
450 feet
5000 feet
1250 feet
20:1
7:1 extending to 150 feet above
runway elevation
Based on maximum wind coverage and
minimum obstructions within the clear
zone and runway safety a rea.
Southwest end of runway located
approximately 1300 feet west-
northwest of powerhouse 1 n tidal
area.
N 53° E, True North
'\J ' ' ....
() l>
J . -::g r . tJ)
C..l -4
Ill ::0 -0 "'C . I ...
0 ...
• .t. ...
--
~ f.ffil ~
z
0 ..
I
,lj .
)
,:;
"'
-• ------····"·--· .. ·-· ..... . .. . --··-----·~-·-----.
RUNWAY SAF!iTY AREA
60' ··--·· . ------· -·-···-... RUNWAY WIDTH
~~·,~c.::;,~~,~--------_l_. [!~--t ·--.·. -. ·... ·-·7---•
-.-.. -~ .. ·•.· ... · .... _.•,·····-········· .••... _.....-... ·._.,.-·-:-;:-.,.,.. . ..,......~-.-. ·_.··· .. ·.· •• ·.-._ ... · ._ .. _ •. ·.·· .. ·_.·. ·.···_.··._.·.·.·._.·._·.· .. · .. ·•·.· .•.. • •.•.•••.... ·.·· ...• _.· ....• • .. ·· ... ·•·· ....• ··•·· ..... ······_ ....•......•.. ···----'•('R~' /'-fHPflAI
"''.....--""'~-··· ' .· . :· ... ·.· ·.: ~ _ . __ __ .....--/ . . -~ 1_-·---rf· .... •· p ::s p co;. 1•!~0TIO N 7:>( -•'' GRIIDEI-.~5.6 ~-/_.---~ · .. ,,, __ .. >·" :· ........ ,. ·.":. :, • / '7?,~~::,_-7 /l¢~;;4-)1'/7 ' w~~ ' -v.<jw ' /;;:;;.v?,~»k-m~~~
PHASE II CONST. /
TUIHiEL CUTTIIHiS
/
TYPICAl ftUN\VA V
CROSS SECTION
RUNWAY LENGTH 2200 FT.
•
8/7 10
Item
Wind Coverage
Vertical Alignment
Runway Elevation
Vertical Curvature
Maximum Longitudinal
Grade Change
Sight Distance
Cross-Section
Transverse Slope
Surface
Criteria
86% of time operations are acceptable
with 15 mph cross wind components.
50 year storm and wave run up + 0. 5'
Will not be less than 300 feet for each
1% grade change.
curvature is planned.
No
Not to exceed 2°6, 0°6 planned.
vertical
Any two points 5 feet above the
runway must be mutually visible for
the entire length of the runway.
2% to edge of runway safety area
Rip-rap provided on bay side of
airfield to protect against wave.
damage at 2: 1 slope.
4:1 slope on opposite side of runway.
12" tunnel cuttings crushed with grid
roller.
8/7 11
CLEARING AND GRUBBING RECOMMENDED DESIGN CRITERIA
Clearing and grubbing specifications shall be modeled after State of Alaska
Standard Specification for Highway Construction I 1981.
This specification basically requires that all surface objects I trees 1
stumps, roots and other protruding obstructions be cleared and grubbed.
Stumps outside the construction limits can be left cut off not more than six
inches above ground level.
Merchantable timber, 6" DBH, shall be removed off site to a location
having public vehicular access and sold at auction. Proceeds shall be
remitted to A PA.
Timber, less than 6" DBH: Logs shall be cut into 24" maximum length
sections or chipped. The sections shall be scattered (not piled) in open
areas of the right-of-way to permit rapid drying to prevent bark beattie
outbreak. They shall not be covered by slash, brush, or other residue.
Preferable method of slash disposal will be chipping or hauling to and
burial in a disposal site.
Clearing and grubbing limits for the maximum reservoir level are to the
1200 foot elevation (project datum) contour.
8/7 12
BASIS OF DESIGN -TEMPORARY AND PERMANENT CAMPS
Design Criteria
Snow Load: 65 psf
25 year recurrence interval for Seldovia. From "Alaskan Snow
Loads", USACRREL 1973 and adjusted for ter·rain and climatic
conditions.
Wind Load: 30 psf
1985 UBC, Design charts for 100 mph wind adjusted for terrain and
elevation.
Seismic Zone: 4
1985 UBC
Environmental
Minimum Temperature: -10°F
Maximum Temperature: 85
Heating Degree Days: 11,000
Environmental Atlas Alaska
TEMPORARY CAMP
Location: floodplain of Battle Creek as shown in feasibility reports
Design of camp pad area showing grading, water supply and distribution,
sewage collection and treatment, and aggregate stockpiles.
PERMANENT FACILITIES
Location: Apprcx imately 1000' SW from powerhouse.
Structures: Configured as shown in December 24, 1985 submittal and as
modified Janaury 8, 1986 by APA.
8/7 13
Housing
Duplex housing units -Two each
Two bedrooms, 1-3/4 baths
Three bedrooms, 1-3/4 baths
Single level
Full finished basement, with partitioned areas, 3/4 bathroom
Provision for addition of carports at later date
Arctic entries
Prefinished metal wood grain siding
Ample eaves and wide facias with soffit on bottom of top chord of
trusses
50 year design life
Wood fireplace
Freezer
50':t separation between duplexes
All electric
Office/Dormitory
Exterior dimensions/architectual features same as duplex (2800 sf)
6 private bedrooms
Central bath on 2nd floor
Two bath rooms on 1st floor, shower in women s
One kitchen area (mess/social)
Office area
All electric
50' minimum to closest duplex
Two story
8/7 14
Shop/Garage/Warehouse
Steel building, 14' eave height
All electric
8,000 square feet
Outside Storage Area -Deleted
8/7 15
BASIS OF DESIGN -UTILITIES
TEMPORARY CAMP
Water System:
Design Population: 300
\Vater Use: 65 gallons/capita/day
Minimum Well Yield: 27 GPM (based on 12 hrs/day pumping)
No. \Veils: 2
Well Configuration: 8" gravel packed well with submersible pump.
\Veil Location: 1 at test well, 1 towards Battle Creek on camp side of
road to dam.
System Configuration: We will design for installation of 2 water
wells. Camp contractor is responsible for
providing all facilities downstream from well
pump discharge piping. This will include
elevated storage (hillside location) or ground
level storage and pressure system.
Contractor furnished facilities shall meet the
following minimum standards:
l nstantaneous Demand: 270 G PM ( 1)
Equalizing Storage: 33,000 Gallons (2)
Fire Flow/Storage: None
Emergency Storage: None
( 1) "Community Water Systems Source Book" by Hveem
(2) "Suggested Practice for Small \Vater Systems" by Alaska Department of
Environmental Conservation. This indicated storage capacity may
vary depending upon final well capacity.
,';,..,~. \. c;n
~AJil
8/7 16
Sewer System:
Design Population: 300
Wastewater Flow: 65 GPCPD
Design Flow: 19,500 gallons/day
Sewage Treatment: Secondary
System Configuration: Aerated lagoons followed by chlorination and
Solid Waste
a polishing lagoon, followed by discharge to Battle
Creek. Lagoon detention time will be approximately 30
days. Lagoon will be divided into two sections,
primary and secondary. Aeration will be by bubble
from pipes placed on lagoon bottom. Air will be
supplied by 3 blowers, arranged and sized so that
100% backup capacity is available. Chlorination will
have a 60 minute detention time. Polishing lagoon
detention time will be approximately 2 days.
Incinerator adequate to serve temporary camp facilities. Ash residue
will be disposed of at a sanitary landfill.
Power, Fuel Storage
Conceptual
developed.
configuration and performance specifications to be
Power facilities will remain at camp site for first 30 days
of Phase II contractor's contract.
Water System:
Water Use: 100 G PCPD
Design Population:
Duplexes 2 x 1 = 14
Office/Dorm = 6
PERMANENT CAMP
20 persons
8/7 17
No. Wells: 2
Fire Protection: Separate system (from powerhouse)
Water System Configuration: Submersible pumps will pump from wells
located near creek between permanent facilities
and powerhouse to tr·eatment facilities (if
required) and storage tank/hydropneumatic
system located in garage/shop/warehouse. Water
will then be distributed to permanent facilities.
Sewage Treatment: Single system serving all permanent facilities. System
will consist of septic tank followed by intermittent sand
filters followed by chlorination and discharge to powerhouse
tail race waters at a point nearest permanent facilities.
Power: All facilities will require power. Final power source will be a
distribution line from powerhouse to permanent camp facilities. Phase
II Contractor will provide generator at a location to be determined by
the Contractor for temporary power.
Solid Waste: Incinerator adequate to serve permanent camp facilities. Ash
residue will be disposed of at sanitary landfill.
Satellite Television: Receiving dish to be located at economical location.
Signal will be provided to duplexes and office/ residences.
Fuel Storage: Fuel tanks will be 2-5000 gallon bur·ied tanks, one for
gasoline and one for diesel fuel. Tanks will be located adjacent to
warehouse.
GEOTECHNICAL DESIGN
CRITERIA -PHASE 1
SITE PREPARATION
J.O. No. 15500
ALASKA POWER AUTHORITY
ANCHORAGE, ALASKA
BRADLEY LAKE HYDROELECTRIC PROJECT
GEOTECHNICAL DESIGN CRITERIA
March 24, 1986
(FOR SITE PREPARATION AND PRELIMINARY CIVIL CONTRACT)
2-045-JJ
REVISION: 0
DATE: MARCH 24, 1986
Copyright 1986
Stone & Webster Engineering Corporation
Anchorage, Alaska
GEOTECHNICAL DESIGN CRITERIA
Sect jon
1.0
2.0
3.0
3.1
3 .1.1
3 .1.2
3.1.3
3 .1.4
3 .1.5
3.2
3 .2.1
3.2.2
3 .2.3
3.2.4
3.2 .s
3.2.6
3.2.7
3.2.8
3.3
3.3.1
3.3.2
3.3.3
3.4
3 .s
2-Q45-JJ
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
SUMMARY DESCRIPTION
FUNCTION OR OPERATIONAL USE
ENGINEERING/DESIGN CONSIDERATIONS
SITE GEOLOGY
Soil Conditions
Rock Conditions
Groundwater Conditions
Individual Discontinuities
Seismicity (Preliminary)
SEISMIC DESIGN
Main Dam and Spillway
Intake Structure and Gate Shaft
Diversion and Permanent Outlet Facilities
Power Tunnel and Inclined Shaft
Penstock and Steel Liner
Powerhouse
Middle Fork and Nuka Diversions
Other Project Structures and Facilities
CONTROL OF EXTERNAL GROUND WATER PRESSURES
Foundation Grouting
Foundation Drainage for Slabs on Grade
Tunnel Drainage
TSUNAMI/SEICHE DESIGN
COLD REGIONS CONSIDERATIONS
i i i
v
vi
1
2
3
3
3
4
7
8
10
11
11
12
13
13
13
14
14
15
15
15
16
17
18
18
GEOTECHNICAL DESIGN CRITERIA
Section
4.0
4.1
4.2
4.3
4.4
4.4.1
4.4.2
4.4.3
4.4.4
4.4 .5
4.4.6
4 .4. 7
4.4.8
4.4.9
4.5
4.5.1
4.5.2
4 .5 .3
4.5.4
4 .5 .5
4.5.6
4.6
4.6.1
4.6.2
4.6.3
4.6.4
4.6.5
4.6.6
5.0
Symbols
Tables
Figures
2-Q45-JJ
TABLE OF CONTENTS
(Continued)
ntle
ENGINEERING/DESIGN CRITERIA AND PARAMETERS
APPLICABLE CODES
SWEC CORPORATE CRITERIA
BRADLEY LAKE PROJECT REPORTS
DESIGN LOADS AND CRITERIA
Dead Loads
Backfill Loads
Uplift and Drainage Criteria
Preliminary Seismic Loads
Blasting Criteria
Tunnel Layout
External Loads on Tunnels and Portals
Rock Reinforcement Criteria
Rock Slope Criteria
SPECIAL REQUIREMENTS
Lateral Earth Pressure
Ground-Support Interaction
Individual Footings and Superposition
Hydraulic Considerations
Seepage Control
Cold Regions Requirements
DESIGN PARAMETERS
Basic Data for Excavations in Rock
Basic Data for Foundations on Soil
Basic Data for Foundations on Compacted Fill
Basic Data for Rock Fill ·
Basic Data for Rip Rap
Coefficients of Friction
GENERAL DESIGN REFERENCES
iv
20
20
22
24
28
28
28
29
30
32
33
34
36
39
40
40
42
42
43
43
43
44
44
47
50
52
52
53
55
59
61
67
GEOTECHNICAL DESIGN CRITERIA
Table No.
1
2
3
4
5
6
7
8
9
10
11
12
2-Q45-JJ
LIST OF TABLES
Title
Geotechnical Design Criteria for Diversion
Tunnel and Permanent Outlet Facility
Geotechnical Design Criteria for Diversion
Channel Improvement
Geotechnical Design Criteria for Powerhouse
and Substation
Geotechnical Design Criteria for Power
Intake Structure
Geotechnial Design Criteria for Power Tunnel
and Inclined Shaft
Geotechnical Design Criteria for Penstock
and Steel Liner
Geotechnical Design Criteria for Gate Shaft
Geotechnical Design Criteria for Middle Fork
and Nuka Diversion Structures
Geotechnical Design Criteria for Miscellaneous
Structures
Geotechnical Design Criteria for Main
Dam
Geotechnical Design Criteria for Cofferdam
Geotech n i ca 1 Design Criteria for Spill way . , . .,.
v
61
63
65
Later
Later
Later
Later
Later
Later
Later
Later
Later
GEOTECHNICAL DESIGN CRITERIA
figur~
1
2
3
4
5
6
7
2-045-J J
LIST OF FIGURES
Mean Horizontal Response Spectrum
Design Accelerogram
External Loads on Tunnel Liners
Lateral Stress Distribution and Passive and
Active Earth Pressure Coefficient vs. Yield
Ratio
Superposition of Stresses from Adjacent
Footings
Maximum Shear Modulus vs. Vertical Effective
Stress
Shear Modulus vs. Shear Strain
vi
67
68
69
Later
Later
Later
Later
GEOTECHNICAL DESIGN CRITERIA
1.0 SUMMARY DESCRIPTION
In general, the project includes raising the water level in Bradley
Lake with a dam and providing a tunnel to divert water downstream to a
powerhouse some 1200 ft below proposed lake level.
The entire Bradley Lake area consists largely of steeply bedded, weakly
metamorphosed, gray, fine-grained graywacke and foliated argillite rock
locally mantled with a thin veneer of overburden, moss, or peat in
poorly drained areas. Within the valleys and lowland beach areas
surrounding the project area, the terra in is covered with glaciers,
outwash materials, tills, talus rubble, bog areas and mud flats.
Several faults are present and 1 nfl uence the 1 ocal topography, tunnel
construction methods, and the seismic activity of the area.
The geotechnical design criteria provides geotechnical parameters and
methods of analyses that are required for the design of structures.
The pertinent data (including cross-references to the Structural Design
Criteria, Hydraulic Design Criteria, design foundation grade,
foundation materials, and groundwater levels) are listed in Tables 1
through 12.
Major structures requiring geotechnical engineering 1 ncl ude the ma; n
dam, which is a concrete faced rockf111 dam with an ungated spillway,
and the power tunnel and penstock manifold system which functions under
high water pressures and passes through several fault zones.
2-045-JJ 1 GEOTECHNICAL DESIGN CRITERIA
2.0 FUNCTION OR OPERATIONAL USE
The Bradley Lake Hydroelectric Project is located on the Kenai
Peninsula in southcentral Alaska approximately lOS miles southwest of
Anchorage, and approximately 27 miles northeast of Homer, Alaska. The
site is located on the southeastern side of Kachemak Bay, in the Kenai
Mountain foothills. This is an area of rugged mountainous topography,
with an irregular coastline and a narrow margin of relatively flat
intertidal mud flats. Bradley Lake is a 1 arge glacial 1 ake fed by
meltwater from Nuka and Kachemak glaciers, and several small alpine
glaciers. Drainage from the lake is by the Bradley River into the
upper part of Kachemak Bay.
The project consists of water diversion facilities, a concrete-faced
rockfill dam at the outlet of Bradley Lake, and an underground power
conduit leading to a surface powerhouse with tailrace discharging into
Kachemak Bay. Additional facilities include a barge basin and docking
facility, air strips, access roads, concrete batching facilities, and
permanent camp. Transmission line facilities will be designed by
others.
The project will develop the hydroelectric energy potential of Bradley
Lake, a natural 1 ake at Elevation 1080 and additional diversion from
the Middle Fork of the Bradley River and from the Nuka Glacier. The
electricity will be transmitted to Homer, the Kenai Peninsula, and
Anchorage.
2-045-JJ 2 GEOTECHNICAL DESIGN CRITERIA
3.0 ENGINEERING/DESIGN CONSIDERATIONS
3.1 SITE GEOLOGY
Preliminary geotechnical investigations have been carried out to
provide an assessment of regional and local geologic conditions. This
has included geologic mapping, reconnaissance for construction
materials, seismic refraction and reflection surveys, exploratory
borings, laboratory testing, water pressure testing, and seismicity
studies. A summary of the information available to date follows.
3.1.1 Soil Conditions
Overburden on the dam axis, power tunnel alignment, and powerhouse
site, varies from less than 1 ft to 20 ft thick, and consists of sands
and silts with angular, highly weathered rock fragments, covered by a
thick mat of organic, mossy material characteristic of the subalpine
tundra. Very thin (1 to 2 ft thick) sandy silty soils form the
overburden for the dam abutments; however, 5 to 25 ft thick tal us and
rubble deposits underlain by sands are found in the river channel
beneath the dam.
Along the proposed access road and power cable alignment, the area
consists of colluvium, talus, till and bogs, with alluvium and tidal
flat deposits along Battle Creek and fn the mud flats. Colluvium
ranges from less than 1 ft to 10 ft thick over rock, may be thicker on
a 1 1 uv 1 al f1 a ts adjacent to streams, and may be as much as 5 ft th i ck
over tal us. Argillite tal us is generally in the 1 to 2 ft size range
with graywacke blocks as large as 15 to 20 ft.
Glacial tills consist of unstratified and unsorted materials ranging
from clay to boulders. Till soils have been found mainly up near the
damsite in the spillway saddle and downstream near the diversion
channel. Seismic profiles and test pits near the spillway saddle show
that the till consists of a boul dery rubble mantled with 5 to 15 ft of
2-045-JJ 3 GEOTECHNICAL DESIGN CRITERIA
soil grading upward to loess. Tills have also been identified near the
Middle Fork diversion, and the powerhouse/penstock portals. Bogs and
muskeg, occurring above Elevation 1000 ft, are typically thin, spongy,
grassy, and peaty with some partially decomposed materials.
The alluvium occurs as bench terraces, fluvial deposits, and as deltaic
deposits near Battle Creek. Concrete aggregate will be obtained from
the soils of the Martin River Delta.
The intertidal deposits are characterized by 2 to 5 ft of soft organic
clay overlain by several feet of finn plastic organic silty clay. A
non-cohesive sand is frequently found beneath the intertidal clays in
the tailrace area to a maximum of 40 ft deep.
3.1.2 Rock Conditions
The project is located in an area of mildly metamorphosed sediments of
Cretaceous age which consist primarily of graywacke and argillite with
minor amounts of interbedded conglomerate, limestone, metavolcanic
rocks, intrusive dikes, and meta-chert beds. High angle jointing and
faulting control many features of the topography, including glacial
scour and erosion. Relatively undeformed sedimentary rocks of Tertiary
age are found to the west. The entire area is part of a major orogenic
belt trending north-northeast parallel to the Aleutian trench. Several
major faults or lineaments parallel to this trend have been mapped in
the vicinity of the site.
Most of the project area is underlain by rocks of the McHugh Complex,
which consists primarily of alternating beds of fine to medium grained
weakly metamorphosed graywacke and foliated to somewhat massive s11 ty
argillite. A minor amount of interbedded meta-conglomerate is
presently with in both the graywacke and the argillite. A few beds of
gray limestone and greenish gray metavolcanic rocks are found on high
c 1 i ffs to the east of the southeast end of Bradley Lake, but they do
not affect the project.
2-045-JJ 4 GEOTECHNICAL DESIGN CRITERIA
The graywacke unit is a light gray to greenish gray rock which consists
primarily of feldspar grains with 5 to 20 percent quartz and 5 percent
or less medium to coarse grained, angular dark gray rock fragments in a
muddy matrix. The graywacke is massive and very hard, and is typically
laced with an irregular network of hairline white quartz and calcite
veinlets. A strong hammer blow is required to break the graywacke and
it commonly fails along irregularly oriented, discontinuous fracture
planes that have a brown to dark gray weathering stain in thin section.
The graywacke occurs in thick massive bodies with occasional interbeds
of argillite or metaconglomerate, and as interbeds, lenses, boudins,
and clasts within the argillite.
The argillite unit of the McHugh complex is a dark gray to black,
indurated, weakly metamorphosed, very fine siltstone with only a small
percentage of clay. These rocks occasionally contain very small
amounts of sand and commonly contain 5 to 10 percent white chert
nodules ranging in size from less than one inch to lenses several feet
across, and as much as tens of feet long. The~ argillite commonly
contains interbeds of graywacke or clasts, lenses, boudins, and erratic
blocks of graywacke which range in size from a fraction of an inch to
several ft in diameter.
Occasional interbeds of metaconglomerate occur within both the
graywacke and argillite of the McHugh Complex. The metaconglomerate
consists primarily of chert clasts. which may compose as much as 70 to
90 percent of the rock mass in a sandy argillaceous matrix. The
metaconglomerate also has a pervasive foliation similar to the
argillite.
The McHugh Complex in the project area is intruded by several dikes of
light greenish-gray dacite. These dikes range in thickness from a few
inches to about 30 ft, and can be traced for several hundred feet.
They are steeply dipping along an east-west strike, across the regional
structural grain at a high angle. Hardness and weathering
characteristics are similar to those of the country rock.
2-045-JJ 5 GEOTECHNICAL DESIGN CRITERIA
Bedding dips steeply to the west throughout most of the project site.
In localized zones, dips are vertical or steep to the east. Contacts
between the two major rock types are typically gradational and exhibit
boudinage or pillow structures of graywacke within the argillite.
Throughout the project area, the argillite has a pervasive steeply
dipping foliation trending N5°E to N200W. In addition; the bedding of
the argillite is often highly deformed into isoclinal folds near the
tunnel alignment.
Jointing patterns were determined from surface geologic mapping and
borehole photography. The daninant joint systems (preliminary) have
been grouped as follows:
Joint Set 1 <Bedding and foliation) -Nl0°E to N300W, 75°E to
esC,.,; close to wide spaced; tight to narrow, clean to chert or
calcite filled; subplanar/slightly rough to smooth.
Jojnt Set 2 -N4SOW to N70°W, 70°NE to 70°SW; moderate] y close to
wide spaced; narrow to open, clean to chert or calcite filled;
en echelon subplanar/sl1ghtly rough.
Jojnt Set 3 -N60°E to E-W, 65°S to 80°N; tight to narrow; low
pe rs fstence; subpl ana r/rough.
Joint Set 4-NS 0 E to N25°E, 2S 0 to 350,.,; tight to open;
subp 1 anar/rough.
Joint Set 5 -NS0°E to N70°E, S0 to lS 0 S; narrow to open;
wavy/rough.
in general order of decreasing prominence.
2-045-JJ 6 GEOTECHNICAL DESIGN CRITERIA
Weathering is generally 1 imited to the top few feet of rock .. and is
closely associated with joints, dikes, and fractures. Surficial
weathering is expressed by a col or change to yellowish-reddish brown.
The rock has the appearance of weathered granite on surface exposures.
Weathering also extends to depth along joints, fractures, and bedding
planes, resulting in weathered clay filling near the surface and slight
yellow to reddish brown stains at depth. Weathering also tends to
accentuate a secondary joint system which does not appear to be
well-developed at depth.
3.1.3 Groundwater Conditions
Groundwater levels presented in Tables 1 through 12 have been estimated
using the following sources:
1. Normal groundwater levels determined from 1985 drilling data.
2. Low groundwater elevations based upon seasonal 1 ow 1 evel s
determined from observation well data and from the invert
elevation of subsurface drainage pipes.
3. Flood 1 eve 1 s date rmi ned using Bradley Lake poo 1 routed PMF
flood level El 1190.6.
Visual reconnaissance suggests most of the rock mass in the vicinity of
Bradley Lake is relatively impermeable to groundwater. Seepage is
apparently limited to joints, fractures, and overburden. Minor seeps
have been identified along the east spillway cliff apparently recharged
by the large area to the north and east of Bradley Lake. Two springs
were identified during geologic reconnaissance. The largest is
associated with Eagle River Fault at the southeast end of the lake.
2-045-JJ 7 GEOTECHNICAL DESIGN CRITERIA
The other spring flows from shallow, unconsolidated soils that cover a
northwest trending 1 ineament near the Bradley River Fault. A
substantial portion of this spring flow appears to be derived from a
small surface stream which flows into talus above the spring. As the
amount of water flowing from the spring appears to be greater than the
stream flow into the talus, it is postulated that additional water
flowing along the fault may contribute to stream flow.
Exploratory borings along the power tunnel and shaft alignment revealed
the presence of deep artesian aquifers. Drillers reported intermittent
gains and losses in the boreholes; near the surface, water gains
appeared to be keyed to open fractures possibly related to glacial
relaxation. Deeper zones exhibited artesian pressures which diminished
with time. Inflows are possible from overlying lakes, but these
probably would drain out and become depleted. It is unknown to what
extent backflushing of dry fractured rock was responsible for artesian
pressures in the deep borings.
3.1.4 Indiyidual Discontinuities
Prominent 11 neaments in the project area are surface expressions of
either joints or faults which have been accentuated by differential
glacial scour or stream erosion. Outcrops needed to reveal the exact
nature of these lineaments are frequently obscured by overburden and/or
vegetation. Major faults were not observed at the dam site or between
the intake and gate structure. Minor shear zones have been identified
near the powerhouse, in the saddle at the right abutment of the
spill way, and near the intake ridge near the proposed rockfill quarry
location. Other minor shear zones have been encountered in most drill
holes, and are probably related to tectonism associated with the Kenai
Mountains uplift.
2-045-JJ 8 GEOTECHNICAL DESIGN CRITERIA
Two major faults intersect the proposed power tunnel alignment. These
are the Bradley River Fault and the Bull Moose Fault.
The Bradley River Fault strikes about N10°E and is vertical. It passes
within 0.7 mile of the proposed dam site. The best exposure is the
point where it crosses the North Bradley River about 2.7 miles north of
the dam site. At that location, the fault zone is about 200 feet wide
and consists of a central zone of rehealed breccia about 50 ft thick,
surrounded by sheared argillite and graywacke which has been rehealed
with calcite. Similar conditions were observed in test borings drilled
along the tunnel alignment. The Bradley River Fault has been traced
from Sheep Creek on the north to as far as 0.8 mile southwest of Battle
Creek, and possibly extends as far south as Dixon Glacier, ·a total
distance of about 12 miles. Outcrops of a dacite dike are offset 1000
ft along the fault in a right lateral sense. Total slip could not be
determined exactly, but observations of slickensides with rakes of 0°
to 23° along the fault suggest that the vertical component of the
displacement caul d be as much as 400 ft. No vi si bl e surface
displacement was
deposits in Sheep
age and overlie
observed in the last 10,000 years. Flood plain
Creek are of Pleistocene (less than 1,000,000 years)
the Bradley River fault. Although no surface
expression of the fault was observed in the til 1, the headscarp of a
large landslide is subparallel to the fault, and is located at or near
the projected fault trace. There is insufficient evidence at this time
to determine if the till is faulted or if the occurrence of the
landslide is related to the Bradley River Fault.
The Bull Moose Fault trends parallel to the Bradley River Fault,
approximately 1.4 miles west of the Bradley River Fault trace. The
Bull Moose Fault strikes N8°E and dips from 67° east to near vertical.
Where exposed north of the tunnel alignment, the fault consists of a
12-ft wide zone of crushed rock with small amounts of clay gouge.
Boreholes along the tunnel alignment showed several shear zones as much
as 24 ft wide. Oblique displacement is suggested by sl fckensides with
a rake of 47°; however, the amount of displacement is undetermined.
2-045-JJ 9 GEOTECHNICAL DESIGN CRITERIA
The Bull Moose Fault forms a strong topographic lineament which has
been traced northeastward for a distance of approximately 7 miles from
the terminus of Dixon Glacier to the mudflats of Bradley River, and
appears to project beneath the unconsolidated flood plain and
intertidal sediments north of the proposed tail race outlet portal.
Surface faulting of recent deposits has not been identified.
Additional faulting in the vicinity of the Bradley Lake Project include
the Eagle River Thrust Fault, and the Border Ranges Fault, as well as
several possible low-angle thrust faults located during reconnaissance
mapping. None of these faults have been identified at the dam site or
along the tunnel alignment.
3.1.5 Seismicity (Preliminary)
Several reports on the geologic and seismic setting of the Kenai
Peninsula are referenced in Section 4.1. Five microseismic stations
and three strong-motion stations have been installed within and around
the Bradley Lake area by the U.S.G.S. These stations are continually
monitored.
The design earthquake study examined possible earthquake sources and
associated maximum magnitude estimates for each source zone.
Probability curves and tabulations of the relative contribution from
various size earthquakes were developed. An analysis of ground motion
parameters was performed and response spectra curves were formulated
for a maximum credible earthquake (MCE), and for ground motions
associated with an earthquake equivalent to 50 percent of the maximum
credible earthquake {the operating basis earthquake, OBE).
Several large regional faults were eliminated from the study because
estimated ground accelerations at the site were found to be relatively
low, compared to other potential source zones. The study was narrowed
down to two regional faults, the Aleutian Mega-Thrust and the Benioff
Zone, and four local faults, the Eagle River, Border Ranges, Bradley
River, and Bull Moose Faults. Both maximum expected magnitude and
2-045-JJ 10 GEOTECHNICAL DESIGN CRITERIA
recurrence intervals were considered. A maximum credible earthquake of
magnitude 8.5 was associated with a regional fault. This would produce
a peak acceleration of 0.55g, with a peak velocity of 55 em/sec; a peak
displacement of 40 em; and a significant duration of 45 seconds.
A maximum credible earthquake of magnitude 7.5 was associated with the
1 ocal faults. Such an event would produce a peak ground acceleration
of 0.75g, with a peak velocity of 70 em/sec; a peak displacement of 50
em; and a significant duration of 25 seconds.
The potential for future fault rupture was evaluated for the Bradley
River, Bull Moose, and minor faults in the vicinity of Bradley Lake.
The evaluation also addressed the possibility of secondary slip to
compensate for primary slip along the Eagle River or Border Ranges
fault. On this basis, the probability of rupture occurring at the
power tunnel over the next 100 years was estimated at approximately 4 x
10-3 , due to either the Bradley River or Bull Moose faults. Along a
min or fault, the probability of rupture is estimated to be
approximately 2 x 10-4 for a 100-year period. Specific design criteria
for various project facilities are discussed in Section 3.2.
3.2 SEISMIC DESIGN
The Bradley Lake Project is located in a seismically active region.
All major p raj act structures w fll be founded on or excavated f n rock.
Design acceleration values given in this design criteria are horizontal
accelerations in rock.
3.2.1 Maio Dam and SpilJwa~
The rna in dam and spillway will be designed for an earthquake with the
response spectrum shown on Figure 1, Mean Horizontal Response Spectrum,
and a normalized peak acceleration of 0. 75g. This corresponds to a
maximum credible earthquake of magnitude 7.5 associated with a local
fault. The field studies conducted to date have not revealed any
2-D45-J J 11 GEOTECHNICAL DESIGN CRITERIA
geologic structure within the project area with a significant potential
for fault displacement. The proposed dam will be designed for this
severe acceleration to retain the reservoir impoundment.
Earthquake resistant design will include removal of alluvium from
beneath the rockfill dam so that the foundation is on rock. Oversize
rockfill is not desirable in the main section of the dam, and will be
raked to the downstream section. Straight toe block foundations will
be excavated for each face slab to intersection of sound rock in the
right and left abutments. Dental excavation and backfill with concrete
will ensure adhesion of the toe block to rock, especially near the
abutnents. Filter zones wfll be designed as bedding material for the
concrete face, and as self-healing filler in the event of seismic
cracking.
Earthquake resistant design for the spillway will include removal of
till and colluvial materials so the foundation is on rock. Grouting
may required for foundation improvement.
3 .2 .2 Intake Structure and Gate Shaft
The intake structure and gate shaft will be designed for an earthquake
with the response spectrum shown on Figure 1, Mean Horizontal Response
Spectrum, and a normalized peak acceleration of 0.7Sg. The intake
gates will be designed to operate after a major seismic event to close
the water passageway of the power conduit.
Earthquake resistant design measures will include increasing the depth
of cover at the portal to 20 ft of sound rock or two tunnel diameters
and increasing the safety factor for slopes to 2.0. In the gate shaft,
a lateral rock load will be chosen from the empirical rock
classification and applied as a pseudo-static 1 ive 1 oad. Immediately
prior to concrete lining the structure, any loose materials will be
scaled from the rock surface and rock bolts will be tightened.
2-045-JJ 12 GEOTECHNICAL DESIGN CRITERIA
3.2.3 Diversion and Permanent Outlet facilities
The diversion and permanent outlet facilities will be designed for an
earthquake with the response spectrum shown on Figure 1, Mean
Horizontal Response Spectrum, and a normalized peak acceleration of
0.75g. The outlet gates will be designed to operate after such a major
seismic event to either remain in their normally closed position in the
water passageway or to open as may be needed to effect reservoir
draw down.
Earthquake resistant design measures will include increasing the depth
of cover at the portals to 20 ft of sound rock or 2 diameters and
increasing the safety factor for slopes to 2.0. The gate shaft will be
designed using pseudo-static live lateral loads chosen from the
empirical rock classification.
3.2.4 Power Tunnel and Inclined Shaft
fully embedded installations will react in concert with the surrounding
rock mass, unless actual rupture and displacement of the rock mass
occurs. The power tunnel will cross the Bradley River and Bull Moose
Faults, each of which have been assumed to be capable of independent
earthquake generation, implying surface and subsurface rupture
potential. In addition these faults are capable of rupture in response
to events on adjacent, larger faults. It is considered impossible to
desi go to withstand or accommodate rock mass rupture. Other than
safety-related issues, no consideration other than those consistent
with normal pressure tunnel design will be applied. In the event
rupture should occur, the power tunnel will be dewatered and repairs
made.
3 .2 .5 Penstock and Steel Liner
The steel liner and penstock and its associated structures will be
designed for an earthquake with the response spectrum shown on
Figure 1, Mean Horizontal Response Spectrum, and a normalized peak
2-Q45-JJ 13 GEOTECHNICAL DESIGN CRITERIA
acceleration of 0.35g. Embedment in rock and design to this seismic
criteria would prevent rupture of the penstock and the uncontrolled
loss of water from the power tunnel.
Earthquake resistant design measures will include increasing the depth
of cover at the penstock portals to 20 ft of sound rock or two tunnel
diameters and increasing the safety factor for slopes to 2.0. The
length of the exposed penstock will be minimized by moving the manifold
underground, and installing rock anchors where necessary to counteract
the pseudo-static 1 ive loads. The steel 1 ined section of the power
tunnel will extend into the mountain to a point at which the overburden
and rock cover (in ft) is at least 60% of the static hydraulic pressure
head.
3.2.6 Powerhouse
The powerhouse will be designed for an effective seismic acceleration
of 0.35g with material stresses not exceeding normal design working
stresses. Dynamic analyses will consider an earthquake with the
response spectrum shown on Figure 1, Mean Horizontal Response Spectrum,
and a normalized peak acceleration of 0.75g with an increase in
allowable material stresses. The powerhouse substructure will be
constructed of concrete securely founded in rock.
Earthquake resistant design measures will include application of
lateral rock loads chosen from the empirical rock classification as a
pseudo-static live load. Immediately prior to concrete pours, any
loose materials will be scaled from the rock surface and rock bolts
will be tightened and fitted with concrete embedment anchors.
3.2.7 Middle Fork and Nuka Diversions
The Middle Fork and Nuka Diversions will be designed for an earthquake
with the response spectrum shown on Figure 1, Mean Horizontal Response
Spectrum, and an effective seismic acceleration of 0.35g. The proposed
dams will be designed for this acceleration to retain the reservoir
impoundment.
2-045-JJ 14 GEOTECHNICAL DESIGN CRITERIA
Earthquake resistant design will include removal of alluvium from
beneath the dam so that the foundation is on rock. Filter zones will
be designed as bedding material and as self-healing filler during
seismic events.
3.2.8 Other Project Structures and Facilities
The other project structures will be designed for an effective seismic
acceleration consistent with Uniform Building Code Zone No. 4.
Some facilities including the dock, roads, and the airfield are founded
on soil or rock formations. Local soil failures are anticipated for
these facilities in the tidal flats during significant seismic events
and will be repaired as needed.
3.3 CONTROL OF EXTERNAL GROUNDWATER PRESSURES
Uplift pressures are equivalent to the full water pressure acting on a
foundation or structure where no head differential exists across the
structure. The foundations and structures will be analyzed for
flotation, if applicable.
3.3.1 Foundation Grouting
The dam and spillway foundations must be stable under all conditions of
construction and reservoir operation, and must 1 imit seepage so as to
prevent excessive uplift pressure, erosion of material, and/or loss of
water. Removal of unsuitable foundation materials for seismic
stability (see Section 3.2) will be supplemented in certain areas by
foundation grouting.
A grout curtain will be constructed under the upstream toe block of the
main dam and along the spillway for a seepage cutoff in rock. A triple
row grout curtain with sequential grouting procedures will be
developed. The maximum depth of the center grout line will be
2-045-JJ 15 GEOTECHNICAL DESIGN CRITERIA
approximately 2/3 of the maximum reservoir hydrostatic head. The
mini mum depth of the center row grout holes will be equal to the slab
width. The grout curtain will be oriented to intersect major joint sets
and will extend upward along the right and left abutments of the dam to
maintain cutoff continuity between the spillway and the main dam.
In effect, the grout curtain will be extended through the main dam knob
by ring grouting within the main dam diversion tunnel and gate shaft.
Three grout rings are anticipated: one at the intake structure to
diversion tunnel transition; a second immediately upstream of the gate
shaft to maintain cutoff continuity with the main dam and spillway
grout curtain; and a third ring circumferentially and along the length
of the gate shaft itself. These grout rings are required to minimize
leakage from the reservoir and promote maintenance of the control
structures. Open joints and concrete contacts will be grouted from
within the diversion tunnel before the upstream rock plug is excavated.
Additional grout curtains are also anticipated along the axis of other
diversion facilities such as rock plug cofferdams, the Middle Fork
Diversion, the Nuka Diversion, and the upstream cofferdam for the main
dam.
3.3.2 Foundation Drainage for Slabs on Grade
Foundation drain holes will be provided for the spillway downstream of
the foundation grout curtain. The drain holes will be drilled into the
foundation rock and extended through the concrete structure to the top
of the agee to permit inspection and maintenance of each drain. The
drain top will include a removable cap. The drains will be connected
by headers and will dis charge downstream of the structure. The header
outlets will be accessible for clean-out if required. The uplift
pressures under the spill way will be considered across the complete
rock/concrete interface varying linearly from the headwater elevation
at the upstream face or heel to the projected piezometric pressure
2-045-JJ 16 GEOTECHNICAL DESIGN CRITERIA
elevation at the line of drains to the tailwater elevation. The
projected piezometric pressure is based upon the effectiveness of the
drainage system expressed as drain efficiency.
The spillway aprons, wing walls and slabs on grade will be designed for
uplift conditions, including sudden changes in water level, if
applicable. Drainage may be provided to equalize the water pressure on
each side of the slab or wall when differential pressures must be
minimized.
3.3.3 Tunnel Drainage
The tunnel linings will be designed for uplift and ambient hydrostatic
conditions resulting from dewatering of the tunnel for inspection
and/or repairs. This will be accomplished by drilling drain holes
through the 1 iner or by channeling behind the 1 iner to sub-invert
drainage pipes. Excess leakage into tunnels will be minimized by
eliminating drain holes where alternative pressure control measures
such as waterproofing are specified. Where tunnel muck is left in
place, such as access adits, periodic cutoff trenches and longitudinal
drains cleaned out to sound rock will be filled with gravel to relieve
the uplift pressure.
The penstock and steel 1 i ner will be designed to prevent collapse
during sudden dewatering of the power tunnel. Drainage of the rock
mass will be accomplished by longitudinal penstock header pipes
embedded in the concrete between the steel 1 iner and the rock. Drain
holes will be drilled into rock at regular intervals for collection by
the penstock drains. Tapped drill holes will be provided in the steel
liner for drilling drain holes into rock after completion of all crown
grouting. Suitable removable plugs will be installed at the outlet of
the penstock drains and within the power tunnel itself for maintenance
and cleanout of mineral deposits.
2-045-JJ 17 GEOTECHNICAL DESIGN CRITERIA
Drainage considerations also govern the selection of tunnel grades used
in the design criteria. Tunnels will be sloped upward from the
portals so that groundwater seeping into the tunnel will drain away
from the heading by gravity. Excess water at the heading interferes
with drilling and blasting the bottom lifter holes and will compact the
muck making it more costly to excavate. <Economies are also gained by
transporting the loaded muck cars at a slight downward grade from the
face.) For ra i1 car mucking, the grade must be such that excess water
does not build up on the rails. Maximum grades, on the other hand, are
governed more by the type of mucking equipment selected than by
drainage considerations. An evaluation of wet conditions will be made
for optimizing equipment selection so that design grades are not
restrictive.
3.4 TSUNAMI/SEICHE DESIGN
(Later-includes reservoir stability)
3.5 COLD REGIONS CONSIDERATIONS
In addition to the traditional soil and rock mechanics problems
associated with design and construction of dams and powerhouse
structures in more temperate climate, the setting of the Bradley Lake
site requires special consideration of seasonal freezing and thawing
problems. Large areas of the reservoir shoreline, as well as the dam
and its rock abutments, are subject to freezing and thawing. Testing
results will be used to evaluate the susceptibility of site materials
to frost action and to measure the permeability, shear strength and
compressibility characteristics of frozen and unfrozen material.
Unsuitable materials exposed to such conditions will be excavated and
replaced with free-draining backfill under and adjacent to structures.
Uncertainty as to the freeze-thaw durability of thin shotcrete layers
restricts its potential use as slope and berm protection. Similarly,
rock slope drains which are exposed to freezing will not function as
2-045-JJ 18 GEOTECHNICAL DESIGN CRITERIA
intended and may aggravate stability. Since concrete mixes can be
designed for cold and harsh environments, they will be used wherever
possible to resist freezing pressures.
Frost action affects the engineering service of rock used as a
construction material. Riprap experiencing alternating wetting and
drying cycles in winter may be susceptible to frost damage depending on
porosity and pore size. Laminated rock may scale badly when water
freezes in open bedding or cleavage planes. Thermal expansion and
contraction of rock is controlled more by presence of moisture than by
properties of the materials.
Additional measures to reduce frost heave will include sloping the
excavations away from structures to prevent surface infiltration.
Grouting of open rock joints may also be necessary to reduce ice
wedging in certain areas.
Although the Bradley Lake project geographically 1 ies within
discontinuous permafrost, no permafrost has been discovered at the main
dam site.
2-045-JJ 19 GEOTECHNICAL DESIGN CRITERIA
4.0 ENGINEERING/DESIGN CRITERIA AND PARAMETERS
4.1 APPLICABLE CODES, REGULATIONS AND GUIDES
Where specific standards and design criteria are not covered in these
criteria, the latest edition of the following codes and standards will
apply:
BATF
COE
COE
COE
OOE
COE
Bureau of Alcohol, Tobacco & Firearms-Various
regulations regarding explosives use and blasting
Engineering and Design (of) Tunnels and Shafts in Rock;
U.S. Army Corps of Engineers, Engineer Manual
EMlll0-2-2901
Recommended Guidelines for Safety Inspection of Dams,
U.S. Army Corps of Engineers
Earth and Rock Fill Fill Dams General
Construction Considerations; U.S. Army
Engineers, Engineer Manual EM 111Q-2-2300
Design
Corps
and
of
Engineering and Design Stability of Earth and Rock-Fill
Dams; U.S. Army Corps of Engineers, Engineer Manual EM
1110-2-1902
Sliding Stability for Concrete Structures; U.S. Army
Corps of Engineers. ETL 1110-2-256, 24 June 1981
NAVFAC DM-7.1 Design Manual-Soil Mechanics, Foundations, and Earth
Structures, Dept. of Navy, Naval Facilities Engineering
Command, 1982
NAVFAC DM-9 Cold Regions Engineering, Design Manual; Dept. of the
Navy, Naval Facilities Engineering Command, March 1985
NAVFAC P-355 Seismic Design for Buildings; Technical Manual, Dept. of
the Army, Navy, and Air Force, 1982
2-045-JJ 20 GEOTECHNICAL DESIGN CRITERIA
PTI
ASTM D1557
ASCE
ASCE
ASCE
ASCE
ASCE
ACI 336.2R
ACI 336.3R
2-045-JJ
Post-Tensioning Manual; Post-Tensioning Institute
8merjcao Society for Testing and Materials
1978 Moisture-Density Relations of Soils Using
10-Lb Rammer and 18 In Drop (Modified
Proctor Density}
American Society of Civil Engineers
Current Trends in Design and Construction of
Embankment Dams; American Society of Civil
Engineers, 1979
Concrete Face Rockfill Dams -Design, Construction,
and Performance; American Society of Civil Engineers,
1985
Guidelines for Tunnel Lining Design; American
Society of Civil Engineers, 1984
Grouting in Geotechnical Engineering; American
Society of Civil Engineers, 1982
Subsurface Investigation for Design and
Construction of Foundations of Buildings; American
Society of Civil Engineers
1966
1972
American Concrete Institute
Suggested Design Procedures for Combined
Footings and Mats
Suggested Design and Construction Procedures
for Pier Foundations
21 GEOTECHNICAL DESIGN CRITERIA
ACI 506 1966 Recommended Practice for Shotcreting
ACI SP-45
ACI SP-54
1974
1976
Proceedings of the Engineering Foundation
Conference on Use of Shotcrete for Under-
ground Structural Support, ASCE/ACI
Proceedings of the Engineering Foundation
Conference on Shotcrete for Ground Support,
ASCE/ACI
If there is, or seems to be, a conflict between this design criteria
and a referenced document, the matter shall be referred to the Lead
Geotechnical Engineer.
4.2 SWEC (X)RFURATE CRITERIA
Required geotechnical calculations for the Bradley Lake Project are
identified in Geotechnical Technical Procedure No. GTP-8.1-0 as
follows:
Title
1. Lateral Earth Pressures
2. Relative Motion During Earthquake
3. Settlement Analysis
4. Heave or Rebound of Excavation
5. Bearing Capacity
6. Stability of Structures
7. Design Groundwater Levels
8. Field Packer Test Data
9. Slope Stability
10. Seepage Analysis
11. Foundation Systems
12. Earth Support System
13. Rock Support System
2-045-JJ 22
Cross Reference
GTG-6.15
GTG-6.4 and GTP-6.1
GTG-6.7
GTG-6.11 and GTP-6.2
GTG-6.8
GTG-6.12 and 6.13
None
GTG-6.19
GTG-6.16 and 6.17
ST-218
None
None
ST-212 and ST-214
GEOTECHNICAL DESIGN CRITERIA
Title Cross Reference
14. Dewatering System ST-218
15. Tunnel Support System None
16. Embankments {includes fill dams) GI-018 and GT-055
17. Analysis of Shoreline Structures None
18. Erosion Protection None
19. Circulating Water Systems None
20. Design of Grout Curtains Inspectors' Manual
These calculations support the Geotechnical Design Criteria which meet
the requi cements of GTP-8. 2-0 and GTP-8.3-0. All geotechnical
procedures CGIPs) and geotechnical guidelines {GIGs) are contained in
the document:
SWEC, "Geotechni ca 1 Division Techn i ca 1 Procedures and Techn i ca 1
Guidelines", latest version.
In the cross referenced list above, GT-xxx refers to qualified
Geotechnical Division computer programs, and ST-xxx refers to qualified
Structural Division computer programs used extensively for solution of
seotechnical problems. "Inspectors' Manual" refers to the document:
SWEC, "Inspectors' Manual. Drilling and Grouting Procedures and
Field Techniques".
The following Engineers' master specifications or applicable portions
thereof shall be considered in conjunction with this design criteria.
00000-G002F Sediment and Erosion Control During Construction
OOOOO-G002L Soil and Rock Excavation
00000-G002M Drilling and Cement Grouting
00000-G002Q Earth Fill
00000-G002S Rock Blasting
2-045-JJ 23 GEOTECHNICAL DESIGN CRITERIA
OOOOO-G002T
OOOOO-G002U
ooooo-Goo3E
OOOOO-S203A
OOOOQ-S203C
OOOOO-S203E
OOOOQ-S203H
Rock Reinforcement
Reinforced Shotcrete
Rock Tunnelling
Mixing and Delivering Concrete
Placing Concrete and Reinforcing Steel
Reinforcing Steel
Concrete Testing Services
4.3 BRADLEY LAKE PROJECT REPORTS
In general, the site or region specific design parameters in this
design criteria are based upon the applicable sections of the following
documents:
1. The following Alaska Power Authority documents:
2-Q45-JJ
a. Alaska Power Authority CAPA}, Bradley Lake Hydroelectric
Project Recommended Design Criteria, July 30, 1985.
b. Best Management Practices Manual, Alaska Power Authority
Document APA-BMP, Susitna Hydroelectric Project, Frank
Moolin and Associates, 1985.
c. Drainage
Alaska
Structure and
Power Authority
Waterway Design Guidelines,
Document APA-DS, Susitna
Hydroelectric Project. Harza-Ebasco. 1985.
d. McGillivray, J., and 0'Hawley, J., literature Review:
Earthquake-Resistant Design of Dams and Cold Weather
Construct ion, prepared for Susitna Hydroelectric
Project, Acres American Inc., JuneS, 1981.
e. Civ i1 & Facilities Design Criteria, Bradley lake
Project; R&M Consultants, Inc., Anchorage, Alaska, 1985.
24 GEOTECHNICAL DESIGN CRITERIA
2. Stone & Webster Engineering Corporation <SWEC). Bradley lake
Hydroelectric Power Project, Feasibility Study, Volume I,
SWEC, Anchorage, Alaska, October 1983.
3. Dryden & laRue Consulting Engineers <D&L). Feasibility Study
of Transmission line System, Phase 1, Bradley lake
Hydroelectric Power Project, D&L, Anchorage, Alaska, August
1983.
4. The following government agency reports:
2-045-JJ
a. U.S. Army Corps of Engineers <COE). Bradley lake
Hydroelectric Project, General Design Memorandum. COE,
General Design Memorandum No. 2, February 1982, Volume 1
of 2.
b. U.S. Army Corps of Engineers <COE). Bradley lake
Hydroelectric Project, General Design Memo rand urn. COE,
General Design Memorandum No. 2, February 1982, Volume 2
of 2.
c. U.S. Army Corps of Engineers (COE). Final Environmental
Impact Statement, Bradley lake Hydroelectric Project,
COE, Alaska District, August 1982.
d. U.S. Army Corps of Engineer <COE). Feasibility Report
for Hydroelectric Power Development of Bradley Lake,
Kenai Peninsula, Alaska. COE, Alaska District,
September 1975.
e. U.S. Army Corps of Engineers (COE). Reanalysis of the
Bradley lake Hydroelectric Project. COE, March 1978.
25 GEOTECHNICAL DESIGN CRITERIA
f. Stephens, C.D., Lahr, J.C. and Rogers, J.A. Review of
Earthquake Activity and Current Status of Seismic
Monitoring in the Region of Bradley Lake Hydroelectric
Project, Southern Kenai Peninsula, Alaska. U.S.
Geological Survey, Open-File Reports 81-736, 82-417,
83-744, and letter transmittal 10/85.
g. Lahr, John c., letter to Alaska Power Authority. 5 April
1985 (status report on Bradley Lake Hydroelectric
Project Seismic Monitoring Program).
h. Hinton, R.B. Soil Survey of Homer-Ninilchik Area,
Alaska. U.S. Department of Agriculture, Soil
Conservation Service, July 1971.
i. Johnson, F.A. Waterpower Resources of the Bradley River
Basin, Kenai Peninsula, Alaska. U.S. Geological Survey
Water Supply Paper 1610-A, 1961.
j. Soward, K.S. Geology of Waterpower Sites on the Bradley
River, Kenai Peninsula, Alaska. U.S. Geological Survey
Bulletin 1031-C, 1962.
k. Karlstrom, T.V., Quarternary Geology of the Kenai
Lowland and Glacial History of the Cook Inlet Region,
Alaskas. U.S. Geological Survey Professional Paper 443,
1964.
1. Pewe, T.L., Quaternary Geology of Alaska. u.s.
Geological Survey Professional Paper 835, 1975.
5. The following geotechnical reports:
2-045-JJ
a. Woodward-Clyde Consultants CWCC). Reconnaissance
Geology, Bradley Lake Hydroelectric Project. Project No.
411931, WCC, Anchorage, Alaska, December 1979.
26 GEOTECHNICAL DESIGN CRITERIA
b. Woodward-Clyde Consultants (WCC). Geologic
Reconna 1 ssance, Bradley Lake Access Road, Project No.
14844A, WCC, Anchorage, Alaska, November 1980.
c. R.W. Beck and Associates (BECK}. Summary Report on
Construction Procedures and Schedule, Bradley Lake
Project. BECK, Seattle, Washington, September 2, 1982.
d. D()IL Engineers <DONU. Bradley Lake Project, Geologic
Mapping Program. DOWL, Anchorage, Alaska, January 1983.
e. Shannon & Wilson, Inc. ( S&W). Bradley Lake
Hydroelectric Power Project, Geotechnical Studies.
K-0631-61, S&W, Fairbanks, Alaska, September 1983.
f. R&M Consultants, Inc. CR&M). Pre-Design Site Conditions
Report of Geotechnical Field Investigations for the
Bradley Lake Hydroelectric Power Project, Phase I
(Summer/Fall 1984), Volumes 1 and 2, R&M, Anchorage,
Alaska, January 1985 and Phase II (Summer/Fall 1985),
Volumes 1 and 2 (in preparation).
6. Laboratory Testing of Rock Samples, Professor A.J. Hendron,
Jr. & Associates and The Robbins Company, Seattle,
Washington, and Atlas-Copco Jarva.
The majority of the parameters in this geotechnical design criteria
were either obtained directly from the above sources or were developed
vi a applicable analytical techniques. There are also several
parameters that can be considered "assumed 11 values and are typically
based upon general empirical data for similar foundation materials.
Specific design values for lateral earth pressure coefficients and
shear moduli have been developed following methods of analyses from
Geotechnical Guidelines 6.15 and 6.1, respectively.
2-045-JJ 27 GEOTECHNICAL DESIGN CRITERIA
Other design values have been developed using methods of analyses from
published literature. The backup for all values presented in these
criteria is contained in the documentation section of the Geotechnical
Design Criteria Book located in the files of the Lead Geotechnical
Engineer for Bradley Lake Hydroelectric Project.
4.4 DESIGN LOADS AND CRITERIA
Environmental loads will be as per the General Project Criteria.
4.4.1 Dead Loads (p)
The following unit weights for dead loads have been established for the
Bradley Lake Project:
Mass Concrete 145 1 bs/ft3
Reinforced Concrete 150 1 bs/ft3
Steel 490 1 bs/ft3
Water 62.4 1 bs/ft3
Ice 56 1 bs/ft3
Salt Water 64 1 bs/ft3
Silt -Vertical 120 1 bs/ ft3
-Horizontal 85 1 bs/ft3
Backfill
-Dry 120 1 bs/ft3
-Saturated 135 1 bs/tt3
-Submerged 85 1 bs/ft3
Rock refer to 4.6 .1
4.4.2 Backfill Loads
The static 1 ateral earth pressure against vertical faces of structures
with cohesionless horizontal backfill will be computed using the
equivalent fluid pressures calculated from:
p = kwH
2-045-JJ 28 GEOTECHNICAL DESIGN CRITERIA
where
p = Unit Pressure
k = Pressure Coefficient
w = Unit Weight of Fill
H = Height of Fill
For structures free to deflect or rotate about the base, the pressure
coefficient will be computed from Rankine's theory, using the following
equation:
2 0 kA = tan (45 -8/2)
Where 0 = angle of internal friction (degrees).
For structures restrained from bending or rotation, the at-rest
pressure coefficient will be used:
k = 1 -sin 0
0
Coulomb's theory will be used for computing lateral earth pressures on
wall surfaces with slopes flatter than 1H:10V or with sloping backfill
steeper than 4H:1V. For critical slopes exceeding 20 ft in height,
detailed slope corrections will be made.
Where vehicular traffic can run adjacent to the structure, a surcharge
loading of 300 lbs/ft2 will be applied; areas subject to crane and
stockpile loads will be checked individually.
4.4.3 Uplift and Drainage Criteria
The load combinations and design groundwater basis as well as the
minimum factor of safety against flotation is 1.1. The loads to
consider in analysis are the dead load (p) as defined in Section 4.4.1
and the buoyant force of the design basis flood.
2-045-JJ 29 GEOTECHNICAL DESIGN CRITERIA
Uplift Cor internal hydrostatic pressure) will be assumed to act over
100 percent of the exposed area of structures. Where no deliberate
drainage is provided, the phreatic surface will be assumed to be no
lower than linear between headwater and tailwater.
Where deliberate drains are provided, the expression for drain
efficiency is:
DE= 100 X CHW-DL)/(HW-TW)
where
DE = Drain efficiency, percent
HW = Headwater elevation, feet
DL = Projected piezometric pressure at the line of drains, feet
1W = Ta i1 water elevation, feet
The drain efficiency will be assumed to be 50 percent with the drains
operative when specific maintenance measures are specified.
The factor of safety against piping due to seepage is the ratio of
critical gradient divided by design gradient.
4.4.4 Preliminary Seismic Loads
The design ground acceleration levels for critical and hazardous
foundations are summarized below (see Structural Design Criteria for
seismic design category). The Maximum Credible Earthquake CMCE) wi 11
be applied to critical structures and the Operating Basis Earthquake
(OBE) will be applied to normal power generating structures.
2-045-J J 30 GEOTECHNICAL DESIGN CRITERIA
Location
Top of rock
Top of ground (if a deep
cohesionless soil overlies
top of rock)
Top of ground (if at least
15 ft of cohesive soil
overlies top of rock)
Horizontal Ground Acceleratjon (g)
J.M.CEl
0.75
Later
Later
J.QB.U
0.35
Later
Later
The design vertical ground acceleration level will be invoked
independently and equals two-thirds of the respective horizontal ground
acceleration.
Pseudo-static seismic loads, in lbs, are computed from the equation:
F = rna
where
a= oriented ground acceleration factor, and
m = weight of potentially moving structure, in lbs.
These forces are conservative because the loads in reality are of
extremely short duration. The mass which is set in motion must be
decoupled from the structure being analyzed in a realistic manner. The
Lead Geotechnical Engineer will review all rock blocks or ground masses
mobilized in the pseudo-static analyses.
For the main rockfill dam, dynamic analyses utilizing seismic loads
will be performed using the SARMA Computer Program (GT-055). Figure 2
shows the Design Accelerogram for the analyses. Shear wave velocities
2-045-JJ 31 GEOTECHNICAL DESIGN CRITERIA
and damping ratios for rock fill will be derived from an earthquake
induced shear strain of 0.1% by means of the Seed and Idriss method
(GTG 6.1). Rock/concrete system damping of 10% will be used for the
toe block structure, as appropriate.
4.4.5 Blasting Criteria
Production blasting will be preceded by a test blasting program away
from the final neat excavation lines to demonstrate acceptable results
with regard to peak pa rti cl e velocity and fragmentation. Cantrall ed
blasting methods will be used for developing tunnel faces and critical
faces shown on the excavation drawings.
Methods used for controlling overbreak will include line drilling,
cushion blasting, presplitting, and smooth wall blasting. ~
drilling consists of drilling nominal 3-in. diameter holes along the
final neat excavation line at approximately 12-in. centers and leaving
the holes unloaded. Cushion blasting consists of drilling line drill
holes as above, but loading them lightly to detach the berm left in
place from shooting the previous row. Presplitt1ng consists of
drilling a single row of holes, loading them 1 ightly with stemming
along the entire length of the hole, and firing the row prior to
blasting the main excavat1on to produce a crack along the line of
presplit holes. Smooth wall blasting consists of drilling a perimeter
row of holes and loading them lightly with low strength explosives and
firing them simultaneously as the last delay period in the round.
Smooth wall blasting will be the method for controlling overbreak in
the tunnel. An allowance of 6-in. overbreak from the neat excavation
line will be used for estimating quantities. The criteria for
acceptance of smooth wall blasted surfaces will be the percentage of
hal f-easts visible. Hal f-easts are the traces of the perimeter row of
holes which are still evident after completion of the blast. When the
percentage of half-casts visible for a given round is unacceptable, the
blast design will be changed within the next two rounds.
2-045-JJ 32 GEOTECHNICAL DESIGN CRITERIA
The charge weight detonated in any single delay of a blast will be
limited so as not to cause damage to the rock outside the neat
excavation line or to any existing structure. Blasting control will be
achieved by 1 imiting the charge per delay such that the peak particle
velocity CPPV as measured by an engineering seismograph) to the most
limiting of the following criteria:
1. PPV not to exceed 2 in./sec at a distance of 120 ft from the
blast.
2. PPV not to exceed 5 in./sec at the structure when the blast
is within 120 ft of the structure.
3. PPV not to exceed 7 in./sec at the structure when the blast
is within 30 ft of the structure.
4. PPV not to exceed 1 in.lsec at fresh concrete, 0 to 11 hrs
age.
5. PPV not to exceed 2 in./sec at green concrete, 11 to 24 hrs
age.
Separate blast control enve~opes wil-l be developed for confined. blasts
(tunnels, shafts, and pits bel ow grade) and for open face blasts.
4.4.6 Tunnel Layout
For preliminary sizing of tunnel excavations, a lining thickness of 1.0
inch per foot of required internal diameter will be assumed.
Absolute maximum grade will be 3.0% (preferably 2.0% maximum) for long
stretches of the tunnel so that rail transport is feasible. Near
portals and shaft intersections the maximum grade will be 1.0%. To
ensure adequate drainage during construction, grades should be not less
than 0.5%.
2-045-JJ 33 GEOTECHNICAL DESIGN CRITERIA
A minimum radius of curvature of 750 ft and preferably 1500 ft for
tunnel alignment will be used for tunnel sections where use of a tunnel
boring machine (TBM) is anticipated. For drill and blast sections
where the TBM is not operating, a minimum radius of 300 ft will be
used.
4.4.7 External Loads on Tunnels and Portals
Rock 1 oads are determined from empirical methods. Near the portals,
full rock cover is taken as rock load with load reductions to one-half
maximum for sound rock. Within the interior sections of control
blasted tunnels under plane strain conditions, one-half to one-quarter
of the empirical rock load is applied to the permanent liner. Figure 3
shows the design external loads for the diversion tunnel. Detailed
lining design will be finalized by the Lead Structural Engineer.
Portal face slopes will be set back with a rock-fall bench and rock
bolted as a minimum. Approach excavations and benches will be dowelled
at the rim and a berm or ditch will be placed to divert surface water
runoff.
Rock loads impose moment, shear, and axial stresses in the tunnel
lining. When rock quality is such that horizontal rock loads exist,
only the excess of vertical load will be considered for the moment
stress. For sensitivity analyses, the fall owing Corps of Engineers
procedure will be used.
The maximum moment, in inch-Jb, for the crown of the circular tunnel
is:
where
M = 0.25 wR 2
w =unit buoyant or dry as applicable rock load, in psi, for
excess vertical rock load
R = radius to the midpoint of the tunnel 1 ining, in inches.
2-Q45-JJ 34 GEOTECHNICAL DESIGN CRITERIA
Moments of equal magnitude but opposite sign occur at the springline of
the tunnel.
Resultant stress in the circular lining, in psi, due to bending moments
is computed from:
where
f 1 = + or -M/S
S =section modulus of the lining, in inch 3
= tension at crown inside face
+ =compression at springline inside face
The compressive axial stress, in psi, is computed from:
where
w = unit buoyant or dry as ap p 1 i cab 1 e rock 1 oad, in psi
Rz = radius to rock, in inches
Rl = radius to inner side of 1 in i ng, in inches.
Compressive stresses due to external hydrostatic pressure are computed
at the inner surface from:
where
p = hydrostatic head at the point of interest, in feet
Then the final stress due to external loads in the tunnel 1 ining, in
psi, is computed from:
2-045-JJ 35 GEOTECHNICAL DESIGN CRITERIA
Safety factors are then computed from the ratio of concrete compressive
strength to final stress due to external loads.
4.4.8 Rock Reinforcement Criteria
Rock reinforcement members include rock dowels, rock bolts, and rock
anchors. Rock dowels are untensioned bars which are simply grouted
into the borehole; the bars may be steel rebars either natural or epoxy
coated, threadbar stock leftover from rock bolting. or fiberglass
dowels. Rock bolts are steel rebars with a threaded end or continuous
rolled thread bar which are stressed typically by torquei ng. ..B.Qs;k
anchors are either high strength rock bolts, or multi-strand tendons
which are highly stressed with a jack. All rock reinforcement members
will be fully grouted or encapsulated with resin for corrosion
protection.
Design of Rock Dowels
Boreholes for rock dowels will be drilled a minimum of 18-inches from
the edge of excavations and will be washed and permeability tested.
The dowels will be centered and supported off the bottom of the hole
during tremie grouting to maintain corrosion protection of the bar.
Lengths will be chosen to intersect the design slope failure plane
projected up from the bottom of the excavation or to support the roofs
of tunnel portals.
Design of Rock Bolts
Design of rock bolts is based on site conditions together with past
experience and empirical rules for detennining the minimum length of
rock bolt, the maximum spacing of pattern rock bolts, and the minimum
average confining pressure to be applied to the rock face. Orientation
of rock bolts will be normal to the rock surface when possible.
2-045-J J 36 GEOTECHNICAL DESIGN CRITERIA
General guidelines are available for rock bolting based on the rock
quality designation (see Table 3-3, Support Recommendations for Tunnels
in Rock based on RQD, COE EllD-2-2901, pp. 3-11 to 3-13>. When pattern
rock bolting is indicated, the following method will be followed.
Select the rock mass quality category from Section 4.6.1 and set the
width of critical blocks from the following table:
WIDTH OF CRITICAL BLOCKS
Rock Mass Qual ity
Sound Rock
Moderately Fractured Rock
Highly Fractured Rock
Excavation Method
Dril 1 and Blast IBM
4. 7 ft 4 ft
2.7
1.3
3.3
2.0
Interpolation may be required; poor rock will require support by means
other than pattern rock bolts.
Rock bolt spacing will be no less than 1.5 x width of critical blocks.
Rock bolt lengths will be no less than the vertical rock load (see
Section 4.4. 7) and will be an even divisor of 60 ft standard bar
lengths when possible. Minimum average confining pressure (p) applied
to the face will be no less than:
where
B = width of excavation
w = b width of critical blocks
Gt = total unit weight of rock (Section 4.6 .1)
in psf.
Rock bolt capacities will be taken as 95% of the yield strength of the
bar and will be stressed to no more than 80% of the yield strength of
2-045-JJ 37 GEOTECHNICAL DESIGN CRITERIA
the bar during installation. If necessary, the minimum average
confining pressure criterion will be satisfied by increasing the bar
diameter or going to grade 150 high strength steel bars.
The length of the resin anchor bond will be determined from resin
ancho;age charts supplied by the manufacturer using 100% of the yield
strength of the bar as maximum anchorage loading.
Design of Rock Anchors
The quantity of rock mobilized will be calculated by using the volume
of pull-out method. Shear resistance between the cone and the
surrounding rock will be neglected. The overlapping of adjacent cones
will be accounted for in the calculation.
Dry weight of rock
Pull-out cone angle
Required submerged
weight of mobilized
rock
Apex of cone or wedge
of mobilized rock
Allowable bond stress
at sound or moderately
fractured rock/grout
contact
= See Section 4.6.1
= 30° from vertical axis
..
= design load of anchor
= located at middle of first
stage grout length
= 160 psi
Each rock anchor tendon will have a first stage grout length in rock
sufficient to resist the proof load of the anchor. This length will be
calculated using the naninal diameter of the hole and the allowable
bond stress given above.
2-045-JJ 38 GEOTECHNICAL DESIGN CRITERIA
Materials
Rock bolt materials will conform to ASTM standards for steel; grade 60
will be used whenever possible. For ease of installation, bars shall
be of the continuous rolled thre9dbar type. Hardened bevelled washers
will be used when the rock surface is not in the plane perpendicular to
the axis of the bolt. Bearing plates of A36 steel will be 318" x 6" x
6" minimum for nominal l-inch bars.
Resin materials will be of the low viscosity type for possible cold
weather application. Fast set resins will be in the 1 to 4 minute
range and slow set resins will be in the 5 to 30 minute range. Cap
plugs for holding the resin cartridges in upward sloping boreholes will
be used prior to bursting and mixing the resin with the threadbar.
4.4.9 Rock Slope Criteria
Rock slopes will be analysed using a two-dimensional sliding plane
analysis with a water filled tension crack. Failure plane angles and
material properties will be provided by the Lead Geotechnical Engineer
on a case-by-case basis.
Preliminary designs of permanent rock slopes may proceed using the
following criteria:~
lH: 2V Grouted Rock Slopes
lH: 4V Sloping Cuts
lH: 8V Sloping Cuts
Rock Quality
Poor to Highly Fractured Rock
Moderately Fractured Rock
Sound Rock
Temporary slopes, depending on safety considerations, may be designed
on the basis of the next higher quality category.
For some intake channel cuts and the powerhouse excavation, pre-set
rock bolts or dowels will be installed prior to blasting to final
2-045-JJ 39 GEOTECHNICAL DESIGN CRITERIA
grade. Slopes may be steepened, provided that sufficient rock
reinforcement is provided. Benches will be provided for slopes greater
than 35 ft in height near portals and other areas where rock falls
would be hazardous.
For critical locations, three-dimensional wedge stability analyses will
be performed.
4.5 SPECIAL REQUIREMENTS
4.5.1 Lateral Earth Pressure
Lateral Forces
The magnitude and distribution of static and dynamic lateral earth and
water forces on essentially rigid, nonyi el ding structures will be
determined according to the criteria shown in Figure 4 <later). For
flexible, yielding structures, the appropriate increases and decreases
in passive and active coefficients are also shown in Figure 4 (later).
The formula developed for lateral stress distribution covers the
general case of the vertical wall with no son-wall friction,
horizontal backfill, and uniform surcharge (for the entire length of
wall). Determination of lateral earth pressures for boundary
conditions different from the above general conditions shall be
performed by the Lead Geotechnical Engineer on a case-by-case basis.
Sliding and Overturning Resistance
Critical or hazardous foundations must be designed to resist sliding
and overturning due to lateral earth pressure, wind, dynamic loads
(seismic, pipe rupture, etc), and waves. Appropriate loading
ccmbinations and minimum allowable factors of safety against sliding
and overturning are presented in the Structural Design Criteria. Load
combinations and safety factors from the latest edition should be
checked prior to performing an analysis for a critical or hazardous
foundation. The applicable criteria at the time of this revision to
the Geotechnical Design Criteria follow:
2-045-JJ 40 GEOTECHNICAL DESIGN CRITERIA
LQsHl
D +
D +
D +
D +
D +
D +
D +
where
Mioirnurn Ea~tQc Qf Safetj:
CQIIIb]OSlt]QD Q~ectuco1og SJ idiog
Ls 2.0 4.0
Ls + E + Lo 1.5 1.5
Ls + w or I 1.5 1.5
Ls + I + w 1.2 1.2
Ls + E' + Lm 1.1 1.1
Ls + W' 1.1 1.1
Ls + w + T 1.1 1.1
D =Dead loads or their related internal moments and
any permanent equipment loads and hydrostatic
loads (under normal operating conditions)
Ls = Static lateral earth pressure
Lo = Dynamic earth pressure {for OBE)
Lm = Dynamic earth pressure (for MCE)
E = Loads generated by the operating basis earthquake (OBE)
E' = Loads generated by the maximum credible earthquake CMCE)
W = Loads generated by the design wind
W' = Loads generated by design storm wave and wind
T = Loads generated by the design tsunami or seiche
specified for the plant (later)
I= Loading from design ice buildup or ice cover on water
surfaces
The case of D + Ls + E + T or W or I is not considered a credible case
on this project. During construction, a factor of safety equal to 1.5
will be used for structures and 1.2 for slopes.
Overturning stability will be analyzed based on cracked-section
analysis and be limited by load-resistance centroid or toe bearing
considerations, as applicable. Normal 1 oad cases will use full
triangular load distributions across the base. Shear resistance safety
factors will be analyzed by:
2-045-JJ 41 GEOTECHNICAL DESIGN CRITERIA
FS = {cA + (S + S )tan 0)}/S n u s
where
c = average unit shear strength on base plane
A = area of the base of the structure
s = summation n of normal forces
s u = summation of uplift forces
0 = angle of internal friction
s s = summation of shear forces
Sliding resistance safety factors will be calculated as:
where
f = friction coefficient between the base and the foundation
material
St = tangential component of forces acting at the base
(including lateral earthquake)
The same equation will be used for downstream wedge sliding analysis,
where the weight of the mass will be equal to the weight of the rock
wedge.
4.5.2 Ground-Support Interaction
(Later-includes tunnel deformation and liner stress design)
4.5.3 Individual Footings and Superposjtjon
In footing design, each footing shall be proportioned to include the
superposition of stresses from the adjacent structures without
exceeding the allowable maximum bearing values.
2-045-J J 42 GEOTECHNICAL DESIGN CRITERIA
The superposition of additional vertical stress imposed on "individual"
footings or other foundations from adjacent structures shall be
computed as shown in Figure 5.
4.5.4 Hydraulic Considerations
Flow velocities are limited to prevent undue erosion and scour of earth
materials. The following allowable flow velocities are suggested:
Normal Ewe cge os;~
Q!leca:tiQo QcawdQWD
Sound bedrock 20 fps 30 fps
Fractured bedrock 10 15
Ri prap channels 6 10
Alluvial channels 4 6
Tailrace/mud channels 1 2
For flow velocities in excess of these, additional treatment of the
surface will be required.
For blasted rock, use a Manning's coefficient value of n = 0.035;
exposed alluvial and riverbank materials will use an n = 0.045.
Ice loads and wave loads will be as per the hydraulic design criteria.
4 .5 .5 Seepage CQn:tcQl
(Later-includes filter design)
4.5.6 CQld RegiQos ReQuicerneo:ts
(Later)
2-045-JJ 43 GEOTECHNICAL DESIGN CRITERIA
4.6 DESIGN PARAMETERS
4.6.1 Basic Data for Excavations in Rock
Results from subsurface explorations and geologic inspections have been
used to detennfne rock qual fty. Based on these results, rock quality
has been categorized as follows:
Rock Mass Quality
Sound Rock
Moderately Fractured Rock
Highly Fractured Rock
Poor Rock
Drill Core
ROD {%}
>75
50-75
25-50
0-25
Fracture
Spacing
>3 ft
1-3 ft
2-12 in.
<2 in.
Excavation at the site can be considered to be in moderately fractured
rock when deeper advance cannot be made by ripping with a backhoe
(exact definition later). All excavations to, and within, rock are to
be inspected and geologically mapped.
Allowable Bearing Capacity {Qa)
For foundations on rock, the allowable bearing capacities are as
follows:
Poor rock
Highly fractured rock
Moderately fractured rock
Sound rock
= 10 ksf
= 20 ksf
= 40 ksf
= 80 ksf
Values presented for allowable bearing capacity are based on minimum
values. Consult Lead Geotechnical Engineer for specific areas; higher
loadings may be acceptable dependent on strain compatibility and
settlement considerations.
2-045-JJ 44 GEOTECHNICAL DESIGN CRITERIA
The recommended bearing value is applicable for all combinations of
load, including dead load plus live load, plus seismic loading or wave
loading or wind loading or tornado loading, whichever is greater.
Strength Parameters (Co, m. s)
For excavations in rock, the unconfined compressive strength (Co, in
psi) follows:
Sound to Poor to
Rock Type
Graywacke
Argillite
Moderately Fractured Highly Fractured
15,000 7,000
8,000 4,000
The rock material parameter (see Reference D07 and D14), m = 5.0 for
sound rock, m = 1.0 for moderately fractured rock, m = 0.25 for highly
fractured rock, and m = 0.005 for poor rock.
The rock size parameter (see Reference D07 and D14), s = 0.1 for sound
rock, s = 0.004 for moderately fractured rock, s = 0.0001 for highly
fractured rock, and s = 0.00001 for poor rock.
Tensile strength will not be included in resisting forces, but will be
considered in tunnel support design.
Deformation Modulus {E)
For computing deformations in rock excavations, the deformation modulus
of the rock mass follows:
Poor rock
Highly fractured rock
Moderately fractured rock
Sound rock
2-045-JJ
=
=
=
=
45
500,000 psi
2 X 10 6 psi
4 X 10 6 psi
8 X 10 6 psi
GEOTECHNICAL DESIGN CRITERIA
Poisson's Ratio (y)
The value of Poisson's Ratio for static loading conditions is v = 0.27.
For dynamic loading conditions, Poisson's Ratio is v = 0.35.
Shear Modulus {G)
The shear modulus for rock is computed from the equation:
G = E I { 2 ( 1 + v) }
Unit Weight (Gt)
The total unit weight of sound rock is 170 pcf. The total unit weight
of moderate] y fractured rock is 165 pcf. The total unit weight of
highly fractured rock is 160 pcf. The total unit weight of poor rock
is 150 pcf. When rock is used to resist uplift or sliding, the total
unit weight is 150 pcf.
Angle of Internal Friction (0)
Based on the results of detailed studies of rock foundation conditions,
as well as laboratory test data and analyses, the following criteria
have been established.
Di scontj nuity
Joints
Foliation planes
Slickensided p 1 anes
a Eeals
40
25
20
~degl f! Re~j dual (degl
35
20
15
For analyses of shear strength through intact rock, an angle of
internal friction, 0 = 50° will be used.
Friction angles for fault gouge or filled joints, cohesion, and
concrete-bedrock adhesion (see Section 4.6.6) will be determined by the
Lead Geotechnical Engineer on a case-by-case basis.
2-045-JJ 46 GEOTECHNICAL DESIGN CRITERIA
4.6.2 Basic Data for Foundations on Soil (Preliminary)
General
Three main soil types on which permanent foundations will be
constructed are the upland soils, the talus soils, and the intertidal
soils. The upland soils include the colluvial and glacial till soils
on which the spil Jway slab and wingwall, the powerhouse access road,
and the substation foundations will be constructed. The tal us soils
include compact deposits of talus and coarse grained alluvium. The
jntertj dal soils include the mud flat and tidal flat deposits of
Kachemak Bay on which the tailrace channel and training dikes will be
constructed. Other soil types will require special consideration.
Depths to groundwater are listed in Tables 1 through 12.
Depth of Frost Penetration
Frost heaving of foundations and fills results from expansion of
freezing water. Soils which are poorly drained and frost susceptible
will be removed and replaced with free draining backfill. At the
Bradley Lake Project site, there are severe mi crocl imates as well.
Below elevation 1000, a depth of frost penetration equal to 5 ft will
be used.
Allowable Bearing Capacity (qa)
Allowable bearing pressures for structures founded on soil vary with
the size and shape of footing and with the depth of embedment. To aid
in design, the following criterion is given. For footings with minimum
dimension <B> greater than 4 ft and depth of embedment (D) greater than
4 ft, the nominal allowable bearing capacity is for 10 ksf for tal us
soils, 6 ksf for upland soils, and 3 ksf for intertidal soils. The
determination of bearing capacity for dimensional factors different
fran above shall be performed on a case-by-case basis by the Lead
Geotechnical Engineer. Settlement analyses will be performed for all
soil founded structures si nee settlement may be the control]; ng factor
in foundation design.
2-045-JJ 47 GEOTECHNICAL DESIGN CRITERIA
The recommended bearing value is applicable for all combinations of
load, including load plus live load, plus seismic loading or wind
loading or tornado loading, whichever is greater, excluding structures
below high water level in the tailrace and lake areas.
Shear Strength Parameters
Cohesion will be taken as zero or established by the Lead Geotechnical
Engineer. The angle of internal friction will be taken as 24 degrees
for intertidal soils and as 33 degrees for upland soils in their
undisturbed state.
Unit Weight
The unit weight of in situ soil is a parameter which varies throughout
the deposit. However, based on statistical averages of undisturbed
samples, the following values will be used:
Dry unit weight CGd)
Total unit weight CGt)
Buoyant unit weight CGb)
Upland So11 s
US pcf
130 pcf
68 pcf
Intertidal Sons
lOS pcf
130 pcf
68 pcf
These values will be decreased somewhat to account for void ratio
changes when disturbed or used as 1 ightly compacted backfill (see
Section 4. 6 .3) •
2-04S-JJ 48 GEOTECHNICAL DESIGN CRITERIA
Earth Pressure Coefficients (Ka, Kp. Ko)
The degree of mobilization of active and passive earth pressure is a
function of wall deformation. The relationship between the active
earth pressure coefficient CKa) and the passive earth pressure
coefficient (Kp) versus wall deformation are presented in Figures 4
and 5 (later), respectively. It is important to note that these
relationships have been developed for the conditions of vertical wall,
nonsloping backfill, and no wall friction. The Lead Geotechnical
Engineer will establish values for Ka and Kp for conditions differing
from those assumed above, on a case-by-case basis.
The at-rest coefficient of lateral pressure is K = 0.45 for upland
0
soils and K = 0.60 for intertidal soils. Soils for areas which are
0
surcharged will use a K = 1.00. Natural soils showing evidence of
0
overconsolidation or which have been compacted (see Section 4.6.3) may
exhibit higher values of K as determined by the Lead Geotechnical
0
Engineer.
Shear Modulus (G)
Figures 6 and 7 shall be used to determine shear moduli for appropriate
stress and strain loads. The values determined from Figure 6 (later}
at the appropriate vertical effective stress shall be reduced by the
nondimansional factors in Figure 7 (later) for the appropriate strain
level. For dynamic analyses, a shear modulus value shall be
broad-banded by ±33 percent. Vertical effective stress (Sv) shall be
determined as fall ONs:
where
S = Gt x Hs + Gb x Hw v
Gt = total unit weight of soil,
Hs = depth to the groundwater table (see Tables 1 through 12),
Gb =buoyant unit weight of soil, and
Hw = depth below the groundwater table to point of
interest in the soil profile
2-045-JJ 49 GEOTECHNICAL DESIGN CRITERIA
The potential for slow drainage of water during drawdown will be
considered.
Poisson's Ratio (y)
For static loading conditions (above the groundwater table) use
Poisson's ratio for soil, v = K0 /(l + K0 ). Below the water table when
the soils are undrained, use v = 0.45.
For dynamic loading conditions use v = 0.5.
4.6.3 Basic Data for Foundations on Compacted Fill <Preliminary)
General
Three types of compacted fill will be used at the Bradley Lake Project
for permanent facilities: select granular f111, semi-pervious fill,
and select earthfill. Select granular f111 will be used as a bedding
material for structures requiring drainage or as replacemenet for frost
susceptible soils. Sem1-pervfous fill w111 be used in the cores of
embankments or in cutoff trenches. Select earth fill will be used for
local construction of access roads and embankments. Specific
requirements for rock fill and filter materials are given in Section
4.6.4, and requirements for rip rap are given in Section 4.6.5
This section covers design parameters applicable for select granular
fill and for random fill both placed in conformance with the
specifications. Where applicable, design parameters are given for
select earth fill.
Allowable Bearing Capacity Cqa)
The criteria given for natural upland soil are applicable for
semi-pervious fill.
2-045-JJ 50 GEOTECHNICAL DESIGN CRITERIA
The maximum allowable bearing capacity of compacted select earth fill
will be evaluated separately by the Lead Geotechnical Engineer.
Shear Strength Parameters
Cohesion will be taken as zero and the angle of· internal friction will
be taken as 30 degrees for select granular fill.
Unit Weight
The following unit weights have been established from preliminary
laboratory test results.
Material
Granular Ffll
Semi-Pervious Fill
Select Earth Fill
Random Earth Fill
Optimum Moisture %
6
13
15
20
Optimum Density
Gd (pcf) Gt (pcf)
142 150
122 138
120
105
138
126
The criterion of compaction will be 85%. 90%. and 95% Modified Proctor
Densities. Road fills and lightly loaded areas will be compacted to
85%; normally loaded areas to 90%; and critical support areas and fills
over 20 ft in height will be compacted to 95% of optimum moisture
density.
The Lead Geotechnical Engineer will establish criteria for compaction
requ1rements different from above.
Earth Pressure Coefficients (Ka. Kp. Ko)
The active and passive earth pressure coefficients presented for soil
are also applicable for compacted random and structural fill.
The at-rest coefficient of lateral pressure {Ko) for compacted select
granular fill is K = 0.50.
0
2-045-JJ 51 GEOTECHNICAL DESIGN CRITERIA
Poisson's Ratio (y) and Shear Modulus (G)
The criteria presented for soil are also applicable for all compacted
fill.
4.6.4 Basic Data for Rock F111
(Later)
4 .6.5 Basjc Data for Rip Rap
G~mu:a]
Riprap consists of three main functional categories: armor stone,
graded riprap, and stone protection. Also included in the design of
riprap is the underlayer of gravel subbase which is not technically
riprap. Armor stone is the largest rock generally used for breakwaters
and requires careful field placement. Graded rjprap consists of hard,
dense, durable natural boulders or rock which has been quarried and
sized for a certain purpose. Stone protection generally consists of a
more widely graded coarse grained and cobbly material obtained from
local sources without screening.
Underlayer
When not naturally present, an underlayer of six inches minimum of
well-graded sand and gravel bedding with less than 5% fines will be
required for all riprap. Where riprap is to be placed on fine grained
subsoils, a geotextile filter fabric will be used.
Rock Qual jty
Rock used for riprap will be hard, dense, durable, freeze-thaw
resistant, and well-graded fran maximum to minimum specified sizes.
Use of laminated argillite rock will be discouraged. Dacite and
grey wacke sources for ri prap will be exp1 oited by quarrying when
2-045-JJ 52 GEOTECHNICAL DESIGN CRITERIA
necessary. Elongated pieces of rock will not be used as riprap.
Placement
Minill'llm compaction of the subbase will be required, such as one pass
with full size bull dozers or routing hauling equipment across the
entire width of surfacing. Riprap will be placed by dumping but will
be smoothed by adjusting the rocks to form a stable mass without large
u nf ill ed voids. Hand p 1 ace me nt will not be req u 1 red. Armor stone
will, however, be adjusted by means of backhoes or clamshells to form a
smooth uniform face. Laminated rock will be either removed or will be
adjusted so that the cleavage or bedding planes are not vertical.
Placement will proceed from bottom of slope upward.
Permissible Rock Sizes
Overall thickness including bedding will not be less than 18 inches
with largest permissible rock of 1 cu. ft •. Maximum 1 ift thickness will
be 60 inches for riprap (not armor stone) with largest permissible rock
of 1 cu. yd. Sizing of riprap for wave action will be as per the
Hydraulic Design Criteria.
4.6.6 Coefficients of Friction {f)
The following table presents values of coefficients of friction for use
in stability analyses. These numbers (except for membrane liner
friction coefficients) represent ultimate values and require sufficient
movement for failure to occur. Peak friction factors should be
determined from laboratory analyses.
Materials
Mass concrete against clean
sound rock
Mass concrete against clean
fractured rock
2-045-JJ 53
Coefficient of Friction
0.70
0.65
GEOTECHNICAL DESIGN CRITERIA
Materj al s
Mass concrete against compacted
granular fill
Mass concrete against compacted
semi-pervious fill and upland soil
Mass concrete against compacted
select earth fill
Mass concrete against membrane liner
Static
Kinetic
Formed concrete against compacted
granular fill
Formed concrete against compacted
select earth and semi-pervious fill
Coefficient of Friction
0.55
0.45
0.40
0.60
0.50
0.45
0.30
The Lead Geotechnical Engineer will specify coefficients of friction
for materials not given in the above table.
2-045-JJ 54 GEOTECHNICAL DESIGN CRITERIA
5.0 GENERAL DESIGN REFERENCES
General Design References -Geotechnical
DOl Blaster's Handbook, E.I. duPont de Nemours & Co., Inc.
002 Compressed Air Handbook, Ingersoll-Rand Corp.
D03 Design of Gravity Dams, U.S. Bureau of Reclamation, 1976
D04 Design of Small Dams, U.S. Bureau of Reclamation, rev.
reprint 977
DOS Dictionary of Geological Terms, American Geological
Institute, 1962
D06 Welded Steel Penstocks, U.S. Bureau of Reclamation,
Engineering Monograph #3, Revised 1977
D07 Hoek, E. and Bray, J.W., Rock Slope Engineering,
Institution of Mining and Metallurgy, London, 1981
D08 Bentall, R., Methods of Determining Permeability,
Transmissibility and Drawdown, U.S. Geological Survey
Water-Supply Paper 1536-I, 1963
D09 Deere, D.V., Technical Description of Rock Cores for
Engineering Purposes, in Rock Mechanics and Engineering
Geology, Vol. 1, 1963
DlO Deere, D.V. and Miller, R.P. Engineering Classification
and Index Properties for Intact Rock, Technical Report
AFWL-TR-65-116, Air Force Weapons Laboratory, N.M. 1966
2-045-JJ 55 GEOTECHNICAL DESIGN CRITERIA
Dll Fermans, Oscar J., Jr., Permafrost Map of Alaska, U.S.
Geological Survey, Miscellaneous Geologic Investigations
Map I-445, 1965
D12 Gibbs, Harold J., Estimating Foundation Settlement by One-
Dimensional Consolidation Tests, U.S. Bureau of Reclamation,
Engineering Monograph #13, March 1953
D13 Hendron, A.J., Jr., Mechanical Properties of Rocks, in Stagg
& Zienkiewicz (eds) -Rock Mechanics in Engineering Practice,
John Wiley and Sons, 1968
D14 Hoek, E., and Brown, E.T., Underground Excavations in Rock,
Institution of Mining and Metallurgy, London, 1980
D15 Johnston, G.H. (ed}, Permafrost Engineering Design and
Construction, John Wiley and Sons, 1981
D16 Kenney, C., Current Practice and Research on Protective
Filters for Cores of Dams, presented at 1982 Acres
Geotechnical. Seminar, April 23, 1982
D17 Linardini, V.J., Heat Transfer in Cold Climates, Van Nostrand
Reinhold Co •• 1981
D18 Nichols, H.R., Johnson, C.F., and Duvall, W.I., Blasting
Vibrations and Their Effects on Structures, U.S. Bureau of
Mines, Bulletin 656, 1971
D19 Obert, L., and Duvall, W.I., Rock Mechanics and the Design of
Structures in Rock, John Wiley & Sons, New York, 1967
D20 Proctor, v., and White, T.L., Rock Tunnelling with Steel
Support, Commercial Shearing Inc., 1977 reprint
2-045-JJ 56 GEOTECHNICAL DESIGN CRITERIA
D21 Siskind, D.E., et. al ., Structure Response and Damage
Produced by Ground Vibration from Surface Mine Blasting,
U.S. Bureau of Mines Report of Investigations #8507, 1980
D22 Stagg, M.S., and Engles, A.J., Measurement of Blast-Induced
Ground Vibrations and Seismograph Calibration, U.S. Bureau
of Mines Report of Investigations #8506, 1980
D23 Travis, R.B., Classification of Rocks, in Quarterly of the
Colorado School of Mines, V of 50 #1, January 1955
D24 Zangar, C.N., Theory and Problems of Water Percolation,
U.S. Bureau of Mines, Engineering Monograph #8, April 1953
D25 Winterkorn, H.F. and Fang, H., Foundation Engineering
Handbook, VanNostrand Reinhold Co., 1978
D26 Bickel, J.O. and Keusel, T.R., Tunnel Engineering Handbook,
VanNostrand Reinhold Co., 1982
General Design References-Seismic
SOl Earthquake Design and Analysis for Corps of Engineers Dams,
U. S. Army Corps of Engineers, ER 1110-2-1806, 30 April
1977
S02 Algermissen, S.T., and Perkins, D. M., 1976. A Probabilistic
estimate of Maximum Acceleration in Rock in the Contiguous
United States, U.S. Geological Survey Open-File Report,
76-416, 45 pp.
S03 Algermissen, S.T., Perkins, D.M., Thenhaus, P.C., Hanson,
S. L. and Bender, B.L., 1982, Probabilistic Estimates of
Maximum Acceleration and Velocities in Rock in the United
States, U.S. Geological Survey Open-File Report, 82-1033,
99 PP·
2-045-JJ 57 GEOTECHNICAL DESIGN CRITERIA
S04 Chakrabarti, s., et al., Seismic Design of Retaining Walls
and Cellular Cofferdams, in ASCE Conference on Earthquake
Engineering, Vol. 1, 1970
S05 Hays, Walter W., Procedures for Estimating Earthquake Ground
Motions, U.S. Geological Survey, Professional Paper 1114,
1980
S06 Joyner, W. B., and Boone, D.M., Prediction of Earthquake
Response Spectra, U.S. Geological Survey Open-File Report
02-977
S07 Schnabel, P.B., and Seed, H.B., 1973, Accelerations in Rock
for Earthquakes in the Western United States, Seismol, Soc.
Am. Bull, 62: 501-516
S08 Seed, H.B., Murarka, R., Lysmer, J., and Idriss, I.M, 1976,
Rela·tionships of Maximum Acceleration, Maximum Velocity,
Distance from Source, and Local Site Conditions for
Moderately Strong Earthquakes, Seismol. Soc. Am. Bull.,
66:221-224
S09 Seed, H.B., and Idriss, I.M •• 1982, Ground Motions and Soil
Liquefaction During Earthquakes. Earthquake Eng. Res. Instr.
Monogr., Berkeley, California, 134 pp.
S10 Seed, H.B., and Whitman, R.V., Design of Earth Retaining
Structure for Dynamic Loads, in Earth Retaining Structure,
ASCE
S11 Woodward-Clyde Consultants CWCC). Final Report on Seismic
Studies for Susitna Hydroelectric Project, WCC, Orange,
Calif., April 1982
2-045-JJ 58 GEOTECHNICAL DESIGN CRITERIA
SYMBOLS
A Area
Horizontal base acceleration
a Vertical base acceleration v
8 Width of footing or ex,cavation
b Angle between backfill slope and horizontal
Co
c
D
E
F
FS
f
G
Gd,Gt
Gm
H
Ka
Ko
Kp
L
M
MCE
OBE
m
n
Poe
Ppe
q
qa
ROD
s
2-045-JJ
Unconfined compressive strength
Unit shear strength at zero normal load
Depth of base of footing below ground surface
Deformation modulus
Pseudo-static seismic force
Factor of safety
Final stress in tunnel lining due to rock load
or coefficient of friction
Shear modulus
Unit weight {dry and total) of soil or rock
Maximum shear modulus
Height of fill or rock slope
Active earth pressure coefficient
At-rest earth pressure coefficient
Passive earth pressure coefficient
Length of footing
Bending moment due to rock load
Maximum credible earthquake
Operating basis earthquake
Mass active during earthquake
Manning's Coefficient
Total soil and water "at rest" for static
and dynamic loading conditions
Total soil and water "passive" 1 ateral force
Surface surcharge
Allowable bearing stress
Rock Quality Designation
Section modulus
59 GEOTECHNICAL DESIGN CRITERIA
S Effective vertical stress v
Sn Effective normal stress
T Shear Stress
v Poisson's Ratio
w Unit weight of backfill or Terzaghi rock load
0 Angle of internal friction
2-045-JJ 60 GEOTECHNICAL DESIGN CRITERIA
TABLE 1
GEOTECHNICAL DESIGN CRITERIA
FOR DIVERSION TUNNEL AND PERMANENT OUTLET FACILITY
Cross References to Civil Criteria
Structural Design Criteria
Hydraulic Design Criteria
Design Category (Seismic)
Type of Foundation
Nominal Tunnel Width
Tunnel Length
Design Foundation Grade or Slope
Intake Invert (Slab)
Outlet Invert <Exposed Rock)
Tunnel
Bearing Material
Rock Type
Design Ground Water Level
Design Rock Loads on Structure
Rock Slopes
Design Rock Slope Failure
Angle of Plane
Discontinuity Type
Cohesion
Unsupported Rock Benches
2-045-JJ
Height
Upstream Portal El.
Downstream Portal El.
Rockfall
61
Part 8-Section 1.0
Main Dam Diversion
Critical
Rock
21 feet
400 feet
1064
1063
1%
Sound rock
Graywacke
Figure 3
Figure 3
1H:4V
60°
Cross foliation
1000 psf
30 ft max
1120
1120
10 ft wide
GEOTECHNICAL DESIGN CRITERIA
TABLE 1 (CONTINUED>
GEOTECHNICAL DESIGN CRITERIA
FOR DIVERSION TUNNEL AND PERMANENT OUTLET FACILITY
Rock Dowels
Spacing
Diameter
Rock Bolts (Slopes)
Length
Spacing
Location
Oi ameter
Tension
Rock Bolts (Tunnel)
Length
Spacing
Location
Diameter
Tension
Rock Anchors (Portal)
2-045-JJ
Length
Spacing
Location
Diameter
Tension
62
5 ft max.
1 1 n.
Penetrate failure plane
5 ft max.
Below el 1120
1 in.
30 kips
10 ft
5 ft max.
Arch
1 in.
30 kips
15 ft
4 ft max.
2 ft from perimeter
1-1/4 in.
50 kips
GEOTECHNICAL DESIGN CRITERIA
TABLE 2
GEOTECHNICAL DESIGN CRITERIA
FOR DIVERSION CHANNEL IMPROVEMENT
Cross References to Civil Criteria
Structural Design Criteria
Hydraulic Design Criteria
Design Category (Seismic)
Type of Foundation
Width of Channel
Length of Channel
Design Foundation Grade or Slope
Diversion Tunnel Outlet
Channel Invert
Channel Slope
Bearing Material
Rock Type
Design Flood Water Level
Pool
End of Channel
Design Rock Loads on Structure
Rock Slopes
2-04S-JJ 63
Part 8-Section 1.0
Main Dam Diversion
Non-critical
None
70-ft Average (STA 4+00
to STA 8+84)
varies from 70 ft at
STA 8+84 to
SO ft at STA 10+34
SO ft from STA 10+34
to end of channel
1,244 ft
1063
1060 to 1044
0.33% ( STA 0+90
to STA 8+84)
3.0% (STA 8+84 to
STA 9+84)
4% <STA 9+84
to STA 12+44)
Mode rate 1 y fractured
to sound rock and
river alluvium
Graywacke and mixed
graywacke/argillite
1067
1048
N/A
1H:4V (to STA 10+34)
vertical (from STA 10+34
to end of channel)
GEOTECHNICAL DESIGN CRITERIA
TABLE 2 (CONTINUED)
GEOTECHNICAL DESIGN CRITERIA
FOR DIVERSION CHANNEL IMPROVEMENT
Soil Slopes
Bench Height <Cut and Ffll)
Fall out Benches
Riprap Design Thickness
At Pool
In Channel
2-045-JJ 64
2H:1 V
35 ft max.
10 ft wide
10 ft (horizontal)
5 ft (horizontal)
GEOTECHNICAL DESIGN CRITERIA
TABLE 3
GEOTECHNICAL DESIGN CRITERIA
FOR POWERHOUSE AND SUBSTATION
Cross References to Civil Criteria
Structural Design Criteria
Design Category (Seismic)
Type of Foundation
Size of Foundation
Design Foundation Grade
Substation
Powerhouse
Access Road
Bearing Material
Rock Type
Design Ground Water Level
Natural
Powerhouse
Design Rock Loads on Structure
Rock Slopes
Bench Height
Design Rock Slope Failure
Angle of Plane
Discontinuity Type
Cohesion
Rock Dowels
2-045-JJ
Spacing
Diameter
65
Part B-Section 6.0 & 8.0
Operational
Rock
80-feet wide x 160-feet
1 ong
18
39
60
Moderately fractured
rock
Graywacke and Cherty
Argillite
Top of Rock
Drain at walls above El 18
None
1H:2V or pattern bolted
22 ft max.
50°
Cross foliation
500 psf
5 ft max.
1 in.
GEOTECHNICAL DESIGN CRITERIA
TABLE 3 (CONTINUED)
GEOTECHNICAL DESIGN CRITERIA
FOR POWERHOUSE AND SUBSTATION
Rock Bolts (Slopes)
Length
Spacing
Location
Diameter
Tension
Rock Anchors (Portal)
Length
Spacing
Location
Diameter
Tension
Soil Slope Support
2-045-JJ 66
Penetrate failure plane
5 ft max.
Bel ow El 60
1 in.
30 kips
15 ft
4 ft max.
2 ft from perimeter
1-1/4 in.
50 kips
Gab ions
GEOTECHNICAL DESIGN CRITERIA
C:ALCULA TED FOR MODIFIED ACCELEAOGRAM
NOHMALIZED TO 0 75g 5% DAMPING
KERN COUNTY EARTHQUAKE 7-21-52 FRIULI, ITALY EARTHQUAKE 9-15-76
TAFT LINCOLN SCHOOL TUNNEL (S69E) SAN ROCCO (EW)
SCALE FACTOR = 3.50 SCALE FACTOR 3.18
2.25~--------------------------------------------~----------~------------------------------------~
.......
Cll ._,
z
0
1.88
i= 1.50
ct a: w
..J w
0
0
ct
..J
..:(
a:
1.13
1-0 0.75
w a.
C/)
0.38
~ RESPONSE SPECTRUM
,Jt:' FOR MODIFIED ACCELEROGRAM
BRADLEY LAKE HYDROELECTRIC PROJECT
MEAN RESPONSE SPECTRUM FOR MAXIMUM EARTHQUAKE
(NEARBY SHALLOW CRUSTAL FAULT)
OAMPLING RATIO 0.05
REFERENCE
WOODWARD·CL YDE CONSULTANTS
REPORT: "DESIGN EARTHQUAKE STUDY"
NOVEMBER 10. 1981
o.ool_----L-----L-----~--~~--~~~~~--~~--~~--~j;--~~~--~s-~ 0.00 0.25 0.7f 1.25 1.50 1.75 2.00 2.50 3.00 2.75 2.25 0.50 1.00
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
KENAI PENINSULA BOROUGH,ALASKA
PERIOD (sec)
GEOTECHNICAL DESIGN CRITERIA
MEAN HORIZONTAL RESPONSE SPECTRUM
FIGURE 1
MODIFIED ACCELEROGI1AM OBTAINED FROM THE FOLLOWING TWO ACCELEROGRAMS
Kf:liN COUNTY EARTHQUAKE 7 21 52 FRIULI. ITALY EARTHQUAKE 9-15 76
IIA004 TAFT LINCOLN SCHOOL TUNNEL. COMP S69E AND 1-3-169 ITALY SAN ROCCO. COMP EW
SCALE FACTOR 3.50 SCALE FACTOR = 3.18
0.15 r-----------------------
,......
C) .......
z
0.50
0 0.25
1-
<(
a:
LLJ
..J
~ 0.00
(.)
<(
0 z
:::> -0.25 0 a:
(!)
-0.50
0.00 SEC TO 2.32 SEC OF MODIFIED = 0.00 SEC TO 2.32 SEC OF KERN CO
2.34 SEC TO 4.30 SEC OF MODIFIED = 2.14 SEC TO 4.10 SEC OF FRIUU
4.32 SEC TO 55.14 SEC OF MODIFIED 3.58 SEC TO 54.40 SEC OF KERN CO
THIS PLOT LIMITED TO FIRST 48.0 SECONDS OF THE MODIFIED ACCELEROGRAM
-0.75~--~~;---~~--~~-----L----~------0. 0 0 -'---·---;-:c);"--;:;:-!-;;:;:;-----;:;::'~:----;~::-:---_;__ __ _j
4.00 16.00 24.00 28.00 32.00 36.00 40.00 44.00 48.00 12.00 20.00 8.00
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
KENAI PENINSULA BOROUGH,ALASKA
TIME (sec)
GEOTECHNICAL DESIGN CRITERIA
DESIGN ACCELEROGRAM
FIGURE 2
1190 I FULL HEAD
__11_80
1170
1150
1140 ----
113 0
112_Q
110 0
1090
~_1060
~ROWN &RING •I
GROUT INTAKE
L I-
DESIGN GRADIENT ~LOCATION OF SHAFT
-·-----~----·\ (NOT FINAL)
PATTERN
-SEEPAGE PRESSURE PROFILE AFTER
INSTANT MIG TUNNEL GATES ARE OPENED
\
\
\ L DRY WELL _I J SHAFT t
\
~~lNG ·I
GROUT
\
\
SHAFT t.. _Ff¥b-..j
I-DR A INS
I~
FLOOD TAILWATER
r ~-PAT TERN --ROCK UKP .... _
1180
116Q_
1140
1120
1080
1060
MAX
2040 PSF MAX
3400 PSF
MAX
680PSF_ Ng 'typ]:
·.·.• .... ,. I
1---;:;=-r---~---'-:::c....::.---------l PHASE l
4t00
DIVERSION TUNNEL
GRADUAL CHANGE
IN ROCK LOAD
3~00 2+00
MAX ROCK LOADING DIAGRAM
REFERENCE DWG 15500-FY-132A
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
KENAI PENINSULA BOROUGH,ALASKA
USE td =170 LB/FT3
NOTE-
ROCK LOADS MAY CHANGE
IF A MID -TUNNEL
GATE SHAFT
r)S INSTALLED •I
I
-0
~
0
~
1+00 0+00
0 30 60 FEET
I ==:J
GEOTECHNICAL DESIGN CRITERIA
EXTERNAL LOADS ON TUNNEL LINERS
FIGURE 3
DESIGN CRITERIA FOR
CIVIL STRUCTURES
J.O. No. 15500
1-041-md
ALASKA POWER AUTHORITY
ANCHORAGE, ALASKA
BRADLEY LAKE HYDROELECTRIC PROJECT
GENERAL PROJECT INFORMATION AND
CIVIL DESIGN CRITERIA
REV IS ION: 0
DATE: MARCH 21, 1986
Copyright 1986
Stone & Webster Engineering Ccorporation
Anchorage, Alaska
January 9, 1986
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
GENERAL PROJECT INFORMATION
AND
CIVIL DESIGN CRITERIA
TABLE OF CONTENTS
SECTION ITEM ~
1.0 SCOPE 1
2.0 GENERAL PROJECT INFORMATION 2
2.1 Climatology 4
2.2 Reservoir, Diversion, and Tidal Information 5
3.0 REGULATIONS, CODES, STANDARDS AND GUIDES 8
3.1 Local, State, and Federal Codes and
Regulations 8
3.2 Industry Codes, Standards, and
Specifications 9
3.3 Design Guides 11
4.0 CIVIL DESIGN CRITERIA 13
4.1 Material for Civ i1 Works 13
4.1.1 Fill Materials 13
4.1.2 fences and Gates 15
4.1.3 Culverts 15
4.3 .4 Drainage Material 16
4 .1.5 Earth Retention Structures 17
4.2 Design of Civil Works 18
4.2.1 R&M Design Criteria 18
4.2.2 Earth Retaining Structures 19
4.2 .3 Roads and Surfacing 19
4.2.4 Slopes 20
4 .2.5 Culvert Design 20
1-041-md GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
figure No.
1.
2.
1-041-md
Tjtle
Project Location
Airstrip/Powerhouse Wind Rose Diagram
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
1.0 SCOPE
GENERAL PROJECT INfORMATION
AND
CIVIL DESIGN CRITERIA
Page 1
This document provides general project information and civil
design criteria necessary for preparation of designs,
construction drawings, and specifications for the Bradley Lake
Hydroelectric Project. Separate fran this criteria are design
criteria set by R&M Consultants, Inc. <R&M) for roads, bridges,
camp facilities and the barge and harbor facilities and criteria
set by Dryden & LaRue, Inc. <D&U for transmission systems.
Further, criteria developed by other disciplines on the Bradley
Lake Project will be referenced as needed. These criteria when
canbined, constitute the Project Design Criteria.
1-041-md GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
Page 2
2.0 GENERAL PRQJECT INFORMATION
The Bradley Lake Project is a hydroelectric facility being
designed by Stone & Webster Engineering Corporation (SWEC) for
the Alaska Power Authority (APA). The project is located in the
southern portion of the Kenai Peninsula approximately 27 miles
northeast of Homer, Alaska and approximately 105 miles south of
Anchorage, Alaska.
The project initially will develop a nominal 90 MW capacity. The
powerhouse will be located on Kachemak Bay with a power tunnel to
Bradley Lake. Bradley Lake is a natural lake with existing water
1 evel at El evatfon 1080, with additional catchment from
surrounding sources. The electricity produced will be
transmitted to Homer, the Kenai Peninsula, and Anchorage.
Certain aspects of the project will be designed so as to not
preclude the installation of a third unit which would result in a
total project capacity of 135 MW.
The project includes the following principal features:
1. A concrete faced rockfill dam approximately 610 feet long x
125 feet high located at the natural outlet of Bradley Lake.
2. A concrete gravity ungated ogee spillway to the side of the
rna in dam.
3. An 18-foot internal lined diameter modified horseshoe-shaped
diversion tunnel approximately 400 feet long adjacent to the
right abutment of the dam, and excavation of the Bradley
River channel immediately downstream of the dam.
4. An 11-foot diameter fully lined power tunnel approximately
19,000 feet long between the Bradley Lake dam and the
powerhouse located on the shore of Kachemak Bay.
1-041-md GENERAL INFORMATION ANO CIVIL DESIGN CRITERIA
Page 3
5. An intake structure with removable trash rack and bulkhead
gates at the damsite.
6. A gatehouse and gateshaft located at the upstream portion of
the power tunnel •
7. Diversion works on the Middle Fork of the Bradley River and
at the terminus of the Nuka Glacier.
8. A steel penstock 1 ocated at the downstream portion of the
power tunnel to the powerhouse, including approximately
2,600 feet of steel tunnel lining.
9. An above ground powerhouse located on the shore of Kachemak
Bay, containing two 45 Md Pelton Turbine Generators and
associated equipment, with capabilities for expansion to
three units.
10. A riprap lined tail race channel discharging into Kachemak
Bay, located downstream of the powerhouse.
11. A Compact Gas Insulated Substation CCGIS) with three llSkV
transformers, located adjacent to the powerhouse.
12. Docking and barging facilities and an airstrip along the
shore of Kachemak Bay.
13. Maintenance and storage facilities.
14. Permanent and construction camp facilities.
15. Access roads within the project area.
16. Permanent housing facilities for operating personnel.
1-041-md GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
Page 4
17. Two 115 kV transmission lines with a switching station
located at Bradley Junction. Bradley Junction is the tie
point to the Homer Electric Association transmission system
located near Caribou Lake.
Work under items 12 through 16 will be performed by R&M
Consultants and work under Item 17 will be performed by Dryden &
LaRue, Inc.
Work for the project will be accomplished in two phases. In
Phase I, the permanent and construction camps, barge facilities,
warehousing, airstrip, roads, the diversion tunnel and intake
structure and the modification to the Bradley River downstream of
the proposed dam will be designed.
Within Phase II, the powerhouse, the dam and spillway, the power
tunnel and penstock, the substation, the Middle Fork and Nuka
diversions, and the permanent release facilities of the diversion
tunnel will be designed.
2.1 CLIMATOLOGY (Figure 1, attached)
1. Latitude: 64.5°
2. Temperature Range: -35°F to +85°F
3. Seismic Zone: UBC Zone 4
4. Wind Speed: max design 100 MPH Coastal, 120 MPH Mountains
5. Mean Annual Precipitation: Varies 40 to 80 inches
6. Approximate Annual Snow Fall: Varies 100 to 200 inches
7. Prevalent wind direction as determined from recent studies
and wind rose data indicates highest speed wind velocities
come from the NNE during cold months and from the SW during
warmer months. (See Figure 2, attached)
1-Q41-md GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
Page 5
2.2 RESERVOIR, DIVERSION, AND TIDAL INFORMATION
THE DATA PROVIDED BELOW IS FOR
INFORMATION PURPOSES AND
MUST BE VERIFIED FOR FINAL DESIGN.
A. DAM & SPILLWAY
1-041-md
DAM PHYSICAL INFORMATION
Type
Dam Crest Width
Dam Crest Elevation
Dam Parapet Crest Elevation
Dam Crest Length
Spillway Crest Length
Spillway Crest Elevation
RESERVOIR LEVELS
Concrete faced rockfill
18 ft. <Inside of Parapet
to edge of dam)
1190 ft.
1194 ft.
610 ft.
175 ft.
1180 ft.
Probable Maximum Flood <PMF) 23,800 cfs (Routed)
Maximum Pool to Pass PMF 1190.6 ft.
Normal Maximum Operating 1180 ft.
Minimum Operating 1080 ft.
Min'imum Possible(@ zero inflow) 1068 ft. (Diversion
Tunnel Drawdown)
Minimum Possible (@zero inflow) 1030 ft. <Power Tunnel
Diversion)
TAILWATER LEVELS
Probable Maximum Flood
Routed Flood of Record
Min'imum Operating
1090 ft.
1067 ft.
1061 ft.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
FLOW DATA
Maximum Lake Inflow (PMF)
Maximum Recorded Lake Outflow
(Natural Channel)
Minimum Recorded Lake Outflow
(Natural Channel)
B. DIVERSION TUNNEL
Fl ow Sect i on { u n 11 ned )
Approximate Length
Design Maxi mum F1 ow
Design Maximum Flow
Operational Minimal Flow
C. MAIN POWER TUNNEL
F1 ow Section
Approximate Length
Design Maximum Flow
D. MIDDLE FORK AND NUKA DIVERSIONS
31,700 cfs.
5210 cfs.
16 cfs
Page 6
21 ft. (Modified Horseshoe)
400 ft.
4000 cfs (During construction)
10,000 cfs (During emergency
draw down)
100 cfs (Through fish bypass
pipes)
11 ft. (Modified horseshoe)
U/S of gate shaft
11 ft. dia. (Circular)
DIS of gate shaft
19,000 ft.
2150 cfs.
1. MIDDLE FORK DIVERSION (Final Design Pending)
PHYSICAL INFORMATION
Dam Height 20 ft.
Crest Elevation 2208 ft.
Dam Length 140 ft.
Spill way Elevation 2204 ft.
Spillway Length 30 ft.
1-041-md GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
RESERVOIR LEVELS
Design F1 ood
Normal Maximum Operating
Minimum Operating <Empty)
TAILWATER LEVELS
Flood
Normal Maximum Operating
Minimum Operating
2. NUKA DIVERSION
(later)
2210 ft.
2204 ft.
2192 ft.
2192 ft.
2192 ft.
2192 ft.
Page 7
E. TIDAL LEVELS
1-041-md
Elevation will be based on project datum.
tabulations below and to Figure 1, attached.
Refer to the
* Highest Storm Surge
Highest Tide <estimated)
Mean Higher High Water
Mean High Water
Mean Sea Level
Mean Low Water
Mean Lower Low Water
Lowest Tide (estimated)
* Estimated 50 Year.
Bradley
Project
Datum
(Ft.)
13.3
11.37
4.78
3.97
-4.02
-12.02
-13.63
-19.63
Bear Cove
Mean Sea
Level (MSU
Datum
(Ft.)
11.67
15.39
8.80
7.99
0.00
-8.00
-9.61
-15.61
Bear Cove
Mean Low Low
Water (MLLW)
Datum
{Ft.)
25.3
25 .a
18.41
17.60
9.61
1.61
0.00
-7.0
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
Page 8
3.0 REGULATIONS, CODES, STANDARDS, AND GUIDES
The following standards, codes, specifications, and guidelines
shall apply; use the editions current at the start of the
detailed design, unless specifically noted otherwise.
3.1 Local, State, and Federal Codes and Regulations
AAC Alaska Administrative Code
OSHA-AI< General Safety Code, Vol. I, II, and III, Occupational
Safety and Health Standards, Alaska Department of Labor,
Division of Occupational Safety and Health, 1973 and as
amended in 1983 and the Construction Code, 1974 and as
amended in 1982.
OSHA-US U.S. Department of Labor Occupational Safety and Health
Administration, OSHA 2206 General Industry Standards (29 CFR
1910), and OSHA 2207 Construction Industry (29 CFR
1926/1910), as they pertain to the work at hand and
supplement the State of Alaska's General Safety Code
identified above.
DOT/PF
DOT/PF
FE~
1-041-md
Alaska Department of Transportation and Public Facilities,
Standard Specifications for Highway Construction, 1981.
Alaska Department of Transportation and Public facilities,
Design Standards for Buildings, 1982 with updates.
Application for license for Major Unconstructed Project,
Bradley Lake Hydroelectric Project, Vol. 1 through 10, by
Stone & Webster Engineering Corporation., for Alaska Power
Authority, 1984.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
Page 9
3.2 Industry Codes, Standards and Specifications
AASHT0-HB
AASHfO
ACI MANUAL
AISC MANUAL
S326
S302
S314
AISI-68
AITC-TM
AITC-100
1-041-md
Specifications for Highway Bridges with updates;
American Association of State Highway and
Transportation Officials (AASHTO), 1978 Edition.
Various AASHTO publications as required.
ACI Manual of Standard Practice Vol. 1 to Vol. 5
American Concrete Institute (ACI), 1985.
Manual of Steel Construction; American Institute
of Steel Construction (AISC), 8th Edition.
Specification for the Design, Fabrication and Erection
of Structural Steel for Buildings with Commentary;
AISC, 1978.
Code of Standard Practice for Steel Buildings and
Bridges; AISC, 1976.
Specification for Structural Joints Using ASTM A325 and
A490 bolts; Research Council on Riveted and Bolted
Structural Joints (RCRBSJ), 1980.
Specifications for the Design of Cold-Form Steel
Structural Members with Commentary; American Iron and
Steel Institute (AISI).
Timber Construction Manual; American Institute of
Timber Construction (AITC), 2nd Edition.
Timber Construction Standard Series (AITC-100, 1972
Series); AITC.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
ASTM
MS Dl.1
~s Dl.4
PWWA
CLFI
MSP-2-81
NEC
NESC
NFPA
SSPC
UBC
1-041-md
Page 10
Various standards; American Society for Testing and
Materials (ASTM).
Structural Welding Code; American Welding Society
CAWS), 1985.
Reinforcing Steel Welding Code; ~s, 1985.
American Water Works Association-various publications
as required.
Commercial Standard for Industrial Aluminum and
Galvanized Steel Chain Link Fencing; Chain Link Fence
Institute (CLFI).
Manual of Standard Practice; CRSI, 1981 with 1983
Supplement.
National Electric Code; National Electrical Contractors
Association, NFPA No. 70-1985.
National Electrical Safety Code, American National
Standard, ANSI C2-l984; Institute of El ectrica1 and
Electronics Engineers <IEEE).
National Fire Protection Association -Latest Guide-
lines and requirements.
Steel Structures Painting Council -Various Guides and
Publications.
Uniform Building Code; International Conference of
Building Officials, 1985 Edition.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
3 .3 DESIGN GUIDES
CRREL
NAVFAC DM-9
Page 11
U.S. Army Corps of Engineers, Cold Regions
Research & Engineering Laboratory Various
Publications.
Cold Regions Engineering, Design Manual; Dept. of
the Navy, Naval Facilities Engineering Command,
1975.
NAVFAC P-355 Seismic Design for Buildings; Technical Manual,
Dept. Army, Navy and Air Force, 1982.
NAVFAC DM-7.1 Design Manual-Soil Mechanics, Foundations, and
Earth Structures, Dept. of Navy, Naval Facilities
Engineering Command, 1982.
APA-DS
EPA-600
APA-BMP
R&M
Criteria
Drainage Structure and Waterway Design Guidelines,
Alaska Power Authority Document by Harza-Ebasco,
Susitna Hydroelectric Project, 1985.
Cold Climate Utilities Delivery Design Manual;
United States Environmental Protection Agency,
1979.
Best Management Practices Manuals, Alaska Power
Authority Document by Frank Moolin and Associates,
Inc., Susitna Hydroelectric Project, 1985.
o Soil and Erosion Control
o Fuel and Hazardous Materials
o Liquid and Solid Waste
o Oil Spill Contingency Planning
o Water Supply
Civil & Facilities Design Criteria, Bradley Lake
Project, R & M Consultants, Inc., Anchorage,
Alaska, 1985.
1-041-md GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
D&L
Criteria
HSDHCP
HCCPH
c~
UA
1-041-md
Page 12
Transmission Facilities Design Criteria, Bradley
Lake Project, Dryden and LaRue, Inc., 1985.
Handbook of Steel Drainage & Highway Construction
Products; American Iron and Steel Institute.
Handbook of Concrete Culvert Pipe Hydraulics;
Portland Cement Association.
Concrete Pipe Handbook; American Concrete Pipe
Association.
Environmental Atlas of Alaska; C.W. Hartman and
P.R. Johnson, University of Alaska, 1978.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
Page 13
4.0 CIVIL DESIGN CRITERIA
The majority of the civil design will be prepared by R&M
Consultants and controlled by their design criteria. Certain
civil materials, not defined by R&M criteria may be used in SWEC
designs, and are defined below. Additionally, minor design
considerations and siting information are included. This
criteria supplements R&M's Design Criteria at present.
4.1 ~ATERIALS FOR CIVIL WORKS
4 .1.1 FILL MATERIALS
Fill material will consist of excavated site materials,
graded and prepared to meet the requirements of the
Geotechnical Design Criteria, and identified below.
A. COMMON FILL
Common fill will be used to construct staging sites and
embankments to final grades; common fill shall not be placed
beneath site structure foundations.
B. SELECT FILL
Select fill consisting of graded site materials will be used
as bedding material for structures requiring drainage and as
replacement for frost susceptible materials beneath
structure foundations.
C. STRUCTURAL FILL
1-041-md
Structural fill consisting of selected and graded material
will be used beneath structure foundations.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
Page 14
D. ROCK FILL
Rock fill will be used in embankments not expected to be
loaded by structures or equipment. For the most part, rock
material used as fill will be developed from the excavations
for structures under criteria set by R&M.
E. RIPRAP FILL
Riprap fills will consist of site rock placed at downstream
ends of drainage pipes, within channels, and at the toes of
designated slopes to dissipate flows, trap silts, resist
wave action and reduce scour. Riprap will meet the
gradation and size limitations of the R&M criteria.
F. CONDUIT AND PIPE BEDDING FILL
Conduit and pipe bedding fill will be manufactured from site
rock, and w111 be graded within the following 1 imits (to be
verified):
u.s. S:taodar:d
2 in.
1 l/2 in.
3/4 1 n.
No. 4
No. 30
No. 200
Si~~e Sjz~ Perceo:t Finer: by Weigh:t
100
90-100
so-as
2S-45
10-25
2-9
G. AGGREGATE FILL
1-041-md
Aggregate fill will consist of rock 3/4 - 1 112 inches in
size. Aggregate fill will be used as insulation fill within
the switchyard, within transformer spill enclosures and
around electrical equipment.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
4.1.2
4.1.3
1-041-md
Page 15
FENCES AND GATES
The substation and switching station, areas around the
powerhouse, local storage areas, safety and hazard related
areas, and security areas will be enclosed with chain link
fences.
Security related areas will be enclosed with 8 ft. high
chain 1 ink fences with "V" bar type extensions carrying a
minimum of two strands of barbed wire on each bar. Chain
link fence posts and fabric shall be installed so as to bury
at 1 east 18 inches min f mum of fabric at the bottom in the
ground to reduce possibility of wildlife intrusion under the
fences.
Protective enclosures, provided in areas where hazards to
personnel demand restricted access but pose no security
problems, will be 8 ft. high galvanized chain link fences,
without barbed wire extensions.
Gates wi 11 be prov 1 ded for access. Vehicle access gates
will be double leafed types capable of a 180 degree swing to
the outside or they may be of the semi-cantilever type.
Minimum width vehicle gates will be 16 ft.
Fences, gates, and hardware will be galvanized and will meet
the Chain Link Fence Institute's "Commercial Standards for
Industrial Aluminum and Galvanized Steel Chain Link
Fencing".
CULVERTS
Materials for culverts will be selected in accordance with
the requirements of the Alaska Power Authority's Drainage
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
Page 16
Structure and Watercourse Design Guidelines. Two types of
culvert material available are corrugated metal pipe (CMP)
and precast reinforced concrete pipe.
A. CORRUGATED METAL PIPE (CMP) CULVERTS
CMP culverts will meet the material requirements of the
latest edition of American Iron and Steel Institute's
publication Handbook of Steel Drainage and Highway Con-
struction Products. Material dimensions will be: thick-
ness, 0.064 inch minimum; corrugations 2-2/3 in. x 1/2 in.
minimum; and diameter 24 in. minimum. Bituminous coating of
CMP will be as required. CMP and hardware will be
galvanized or aluminum coated, as required. Culverts shall
utilize flared end sections.
B. PRECAST CONCRETE PIPE
4 .1.4
Reinforced precast concrete pipe will conform to ASTM C76.
Culvert pipes will be no less than 24 inches in diameter.
DRAINAGE MATERIALS
Materials used in construction of drainage facilities will
be as specified and as identified below, and will follow the
Alaska Power Authority's Drainage Structure and Waterway
Design Guidelines and Best Management Practices Manuals.
A. DRAINAGE GRATING
Drainage grating will be by the Neenah Foundry Co., or
equal.
B. CATCH BASIN FRAMES
1-041-md
Catch basin frames and lids will be by the Neenah Foundry
Co., or equal.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
Page 17
C. FILTER FABRIC
Filter fabric used around drainage pipes, etc., will be by
Mirafi, Fibertex, Phillips or equal. Fabric type and weight
will be specified by the Responsible Geotechnical Engineer.
D. DRAINAGE PIPE
Drainage pipe will be perforated
galvanized corruga1fed metal pipe.
polyvinyl chloride or
All pipe shall include
joint hardware, flares, screens, etc. Drainage pipe will be
wrapped with filter fabric and shall be provided with heavy
duty galvanized wire mesh screens securely strapped over
exposed ends where the pipes daylight, or the ends shall be
plugged and capped.
E. TRENCH COVERS AND MANHOLE COVERS
Trench covers for areas not associated with vehicular
traffic may be minimum 5116 inch ASTM A36 carbon steel
checkered plate. Trench covers located within areas
accessible to vehicles and manhole covers will be Neenah
Foundry Company cast products, or equal.
F. MANHOLES
4 .1.5
1-041-md
Manholes may be precast concrete or cast-in-place concrete
units as availability and design allow.
EARTH RETENTION STRUCTURES
Earth retention structures may be reinforced concrete
retaining walls, metal bin walls, wood, gabions or concrete
cribbed walls, bulkheads, sheetpil ing cofferdams, or
reinforced earth retaining structures.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
Page 18
Materials used shall meet the design and specification
criteria requirements developed by the project. Basic earth
retention structures will also meet the following:
A. BIN WALLS
Metal sheet components will be Armco Bin Wall Products, or
equal. Metal sheet components will be Aluminized Steel Type
2 in conformity with AASHTO M-27 and 80L. All bolts,
fasteners, straps, etc., for walls in corrosive areas will
be stainless steel.
B. REINFORCED EARTH RETAINING STRUCTURES
4.2
4.2.1
1-041-md
Face panels shall be reinforced concrete. Straps will be
per the manufacturer's recommendations, except that in
corrosive
5052-f-82.
situations, straps will be
Fasteners shall be aluminum
aluminum alloy
alloy 6061-74.
Alternate earth retaining wall concepts are acceptable, if
approved by the Geotechnical Engineer.
DESIGN OF CIVIL WORKS
R&M DESIGN CRITERIA
The majority of the civil works will be by R&M Consultants
and will be controlled by their Criteria. Additional
criteria will be developed as required. Where design
concerns soil and erosion control and drainage and waterways
structures, the guidelines APA-DS and APA-BMP will be
followed. Some minimal civil design guidance is included
bel ow.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
4.2.2
4.2.3
A.
1-041-md
Page 19
EARTH RETAINING STRUCTURES
Excessively long fill slopes or abrupt changes in the
contour may require benches to reduce erosion and the use of
earth retention structures. Benching will, as a minimum
follow the USC requirements, unless otherwise controlled by
the Geotechnical Design Criteria or the APA Best Management
Practices Manuals. Earth retention structures will be
designed to the earth pressures and formulation identified
by the Geotechnical Design Criteria.
Solid-type walls will be provided with a perforated CMP or
PVC heel drain, wrapped with an approved filter fabric, and
covered with a well graded, drainable fill. Drain pipe will
extend full length of wall system with exit pipe at ends.
Concrete used for normal reinforced concrete walls, metal
bin wall and reinforced earth structure toe bases will have
a minimum specified compressive strength of 3,000 psi at 28
days.
Concrete used for reinforced earth face panels will have a
minimum specified compressive strength of 4,000 psi at 28
days.
RQADS AND SURFACING
ACCESS ROADS
Minor access roads required by design will follow the R&M
criteria. Exceptions will be made only with the approval of
the Responsible Civil Engineer.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
Page 20
B. RO,A.D SURFACING
4.2.4
4.2.5
1-041-md
Roads wi 11 be surfaced to match major roads where traffic
and load capacity warrant.
It is not anticipated that asphalt paving will be used.
Rock fill will be used to pave selected areas. The
following depths of rock fill shall be used as a minimum:
SLOPES
Access Roads
Substation
Powerhouse Yard Areas
Per R&M
6 in.
6 in.
Slope criteria for embankments, cut and fill slopes and
excavation in rock or earth will follow the requirements of
the Geotechnical Design Criteria as to maximum and minimum
slopes, ditching and toe treatment and requirements for
benching slopes at periodic intervals. Refer to 4.2.2
herein.
CULVERT DESIGN
Only when design of culverts is not a part of R & M's
Contract, will they be designed by SWEC. Flow
characteristics for such culverts shall be provided by the
responsible Hydraulic Engineer. Design loads imposed on the
culverts, minimum fill, etc., will follow R&M Criteria.
Design of any culvert will follow the guidelines and design
procedures developed by the Alaska Power Authority as stated
in the Best Management Practices -Soil and Erosion Control
and Drainage Structures and Waterway Design Gujdel ines.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
1-041-md
Page 21
Additional design guidance is presented in the Handbook of
Steel Drainage & Highway Construction Products, the Concrete
Pipe Handbook, and the Handbook of Concrete Pipe Hydraulics.
GENERAL INFORMATION AND CIVIL DESIGN CRITERIA
~
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-13.63
-19.63
ALASKA POWER AUTHORITY PROJECT LOCATION
BRADLEY LAKE HYDROELECTRIC PROJECT
KENAI PENINSULA BOROUGH, ALASKA FIGURE 1
GENERAL INFORivtATIO"~ & CIVIl. DESIGN RITERIA
NW NNW
WSW I I I F'-I ~.~ ( \ / \ I f'.. /\ \ \ 4 \ \ I T f f "Q 7 v -. \0.4 0.27 " 7 \ 3 2 \ \?"' i 1 1
NE
sw
I\ \ \ .-\( \ \ 6 v.of 'W-\0 '5--Y u.c.; 7' .J I I u.u I I ENE
\ I C? \ tJ 3 \7 "' II 91 · -\ ~ 7 r r I
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
KENAI PENINSULA BOROUGH, ALASKA
MPH SE
GENERAL
AIRSTRIP I POWERHOUSE
WIND ROSE DIAGRAM
FIGURE 2
I NFDf<tvl.ATIQ\J & CIVIL DE..';IGf\J CR ITER lA
STRUCTURAL DESIGN
CRITERIA -MAIN DAM
DIVERSION
2-105-JJ
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J. 0. No. 15500
STRUCTURAL DESIGN CRITERIA
PART A
REVISION: 0
DATE: FEBRUARY 27, 1986
STONE & WEBSTER ENGINEERING CORPORATION
ANCHORAGE, ALASKA
2-105-JJ
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. NO. 15500
STRUCTURAL DESIGN CRITERIA
PART A: GENERAL STRUCTURAL DESIGN CRITERIA
PART B: SPECIAL REQUIREMENTS AND DESIGN
CRITERIA FOR MAJOR STRUCTURES
STONE & WEBSTER ENGINEERING CORPORATION
ANCHORAGEt ALASKA
SECTION
PART A
1.0
2.0
2. 1
2.2
2.3
3.0
4.0
11. 1
11.2
4.3
4.4
4.5
4.6
4.7
4.8
4. 8. 1
4.8.2
4.8.3
4.9
4. 10
4. 11
4. 12
4. 13
4. 14
4. 15
4. 16
4. 17
4. 18
4. 19
4.20
5.0
5. 1
5.2
5.3
5.4
5.5
2-105-JJ
TABLE OF CONTENTS
GENERAL STRUCTURAL DESIGN CRITERIA
GENERAL
REGULATIONS, CODES, STANDARDS AND GUIDES
Local, State, and Federal Codes and Regulations
Industry Codes, Standards, and Specifications
Miscellaneous Documents
MATERIALS
DESIGN LOADS
Dead Loads (D)
Live Loads (L)
Snow and Ice Loads (S,I)
Equipment Loads (M)
Hydraulic Loads (H)
Soil and Rock Loads
Wind Loads (W)
Seismic Loads (E)
General Seismic Conditions
General Seismic Forces
Seismic Forces on Elements
Tsunami and Seiche Induced Forces
Thermal Loads (T)
Pipe and Cable Tray Load Allowances
Roof Truss Load Allowance
Column Load Allowance
Bracing Load
Temporary Roof Loads
Crane Impact Allowance
Hoist Trolley Loads
Truck, Fork Lift, and Cart Loads
Vibrational Loads
Construction Loads
STRUCTURAL DESIGN
Load Combinations
Stability Requirements
Steel Design
Concrete Design
Masonry Design
i
A-1
A-4
A-4
A-5
A-6
A-7
A-10
A-10
A-10
A-10
A-11
A-11
A-11
A-12
A-13
A-13
A-14
A-17
A-18
A-18
A-19
A-20
A-20
A-21
A-21
A-21
A-22
A-22
A-23
A-23
A-21!
A-24
A-25
A-26
A-32
A-33
STRUCTURAL DESIGN CRITERIA
TABLE OF CONTENTS CONI •
SECTION .I.:rm PAGE
~ TABLES A-34
Table 1 Selected Material Weights A-34
Table 2 Minimum Live Loads for Floors and Decks A-35
Table 3 Estimated Equipment Weights A-36
Table 4 Miscellaneous Equipment Loads A-38
Table 5 Snow Loads A-38
Table 6 Wind Pressures -Speed v = 100 mph,
I = 1. 0' Exposure B A-39
Table 7 Wind Pressures -Speed v = 100 mph,
I = 1.0, Exposure C A-40
Table 8 Wind Pressures -Speed v = 120 mph,
I = 1. 0' Exposure B A-41
Table 9 Wind Pressures -Speed v = 120 mph,
I = 1. 0' Exposure C A-42
Table 10 Wind Loads Importance Factors A-43
ii
2-105-JJ STRUCTURAL DESIGN CRITERIA
TABLE OF CONTENTS CONT.
SECTION ITEM PAGE
PART B SPECIAL REQUIREltENTS AND DESIGN
CRITERIA FOR MAJOR STRUCTURES
1.0 MAIN DAM DIVERSION 81-1
2.0 MAIN DAM B2-1
3.0 SPILLWAY 83-1
4.0 POWER TUNNEL AND GATE SHAFT B4-1
5.0 STEEL LINER AND PEN STOCK 85-1
6.0 POWERHOUSE B6-1
7.0 TAILRACE B7-1
8.0 SUBSTATION AND TRANSMISSION SYSTEM 88-1
9.0 MIDDLE FORK AND NUKA DIVERSIONS 89-1
10.0 COFFERDAMS Bl0-1
iii
2-105-JJ STRUCTURAL DESIGN CRITERIA
A-1
PART A
STRUCTURAL DESIGN CRITERIA
1. 0 GENERAL
This document provides structural design criteria necessary to design
the Bradley Lake Hydroelectric Project. Separate from this criteria
are design criteria set by R & M Consultants, Inc. (R & M) for roads,
bridges, camp facilities, barge and harbor facilities and criteria set
by Dryden and LaRue, Inc. (D & L) for transmission systems.
Supplemental to this criteria are, General Project Information and
Civil Design Criteria, Geotechnical Design Criteria, and Hydraulic
Design Criteria.
The Bradley Lake Project is being designed by Stone & Webster Engi-
neering Corporation (SWEC) for the Alaska Power Authority. The project
is located in the southern end of the Kenai Peninsula approximately 27
miles northeast of Homer, Alaska and approximately 105 miles south of
Anchorage, Alaska.
The project will initially develop a nominal 90 MW capacity. The
powerhouse will be located on the Kachemak Bay with a tunnel to Bradley
Lake. The existing natural lake level is at elevation 1080. The
electricity produced will be transmitted to Homer, the Kenai Peninsula,
and Anchorage. The project will be designed so as not to preclude the
installation of a third unit with a resulting total project capacity of
135 MW.
The project includes the following principal features:
1. A concrete faced rockfill dam approximately 610 ft long x 125 ft
high located at the natural outlet of Bradley Lake;
2. A concrete ungated gravity ogee spillway;
2-106-JJ STRUCTURAL DESIGN CRITERIA
A-2
3. A 19 ft diameter by 400 ft long diversion tunnel and excavation of
the Bradley River channel immediately downstream of the dam;
4. A power tunnel approximately 11 ft diameter by 19,000 ft long
between Bradley Lake and the powerhouse located on the shores of
Kachemak Bay;
5. An intake structure with a removable trashrack and bulkhead gates
at the inlet to the power tunnel;
6. A gatehouse and gateshaft located in the upstream portion of the
power tunnel;
7. Diversion works on the Middle Fork of the Bradley River and at the
terminus of the Nuka Glacier;
8. A steel penstock located at the downstream portion of the power
tunnel to the powerhouse;
9. An above ground powerhouse located on Kachemak Bay, containing two
45 MW generators with Pelton turbines and associated equipment
with capabilities for expansion to three units;
10. A riprap lined tailrace channel discharging into Kachemak Bay,
located adjacent to the powerhouse;
11. A Compact Gas Insulated Substation (CGIS) with 115 kV transformers
located adjacent to the powerhouse;
12. Docking and barging facilities and an airstrip at the Kachemak
Bay;
13. Maintenance and storage facilities;
14. Both permanent and construction camp facilities;
2-106-JJ STRUCTURAL DESIGN CRITERIA
A-3
15. Access roads within the project site;
16. Permanent housing facilities for operating personnel; and
17. A 115 kV transmission line with intertie switching station at the
Homer-Soldotna transmission system.
Work under items 12, 13, 14, 15 and 16 will be performed by R & M
Consultants and work under item 17 will be performed by Dryden and
LaRue, Inc.
2-106-JJ STRUCTURAL DESIGN CRITERIA
(
A-ll
2.0 REGULATIONS, CODES. STANDARDS,AND GUIDES
Unless otherwise stated, the design of all structures shall conform to
the latest editions of the applicable codes and specification listed
below. Should a conflict arise between any of the referenced codes,
the matter shall be referred to the Lead Structural Engineer for
resolution.
2.1 LOCAL. STATE. AND FEDERAL CODES AND REGULATIONS
AAC
OSHA-AK
OSHA-US
DOT/ PF 1982
FERC 1984
2-106-JJ
Alaska Administrative Code, Section 13AAC50,
(incorporates UBC provisions for Alaska State
building code requirements).
General Safety Code, Vol. I, II, and III,
Occupational Safety and Health Standards, Alaska
Department of Labor, Division of Occupational Safety
and Health, 1973 and as amended in 1983 and the
Construction Code, 1974 and as amended in 1982.
U.S. Department of Labor Occupational Safety and
Health Administration, OSHA 2206 General Industry
Standards (29 CFR 1910), and OSHA 2207 Construction
Industry (29 CFR 1926/1910), as supplement to the
State of Alaska's General Safety Code.
Alaska Department of Transportation and Public
Facilities, Design Standards for Buildings.
Application for License for Major Unconstructed
Project, Bradley Lake Hydroelectric Project, Vol.
through 10, by Stone & Webster Engineering Corp., for
the Alaska Power Authority.
STRUCTURAL DESIGN CRITERIA
(
(
A-5
2.2 INDUSTRY CODES. STANDARDS. AND SPECIFICATIONS
AASHTO-HB 1978
ACI 302.1R-80 1980
ACI 315-80 1980
ACI 318-83 1983
ACI 318.1-83
ACI 336.2R-66 1966
R1980
ACI 336.3R-72 1972
R1980
AISC 1980
AISI-68
AWS D1. 1 1985
AWS D1.4 1985
2-106-JJ
Standard specifications for Highway Bl'idges;
American Association of State Highway and
Transportation Officials (AASHTO).
Guide to Concrete Floor and Slab Construction.
Manual of Standard Practice for Detailing
Reinforced Concrete Structures.
Building Code Requirements for Reinforced
Concrete (ACI 318) and Commentary (ACI 318R).
Building Code Requirements for Structural Plain
Concrete (ACI 318.1) and Commentary (ACI
318.1R).
Suggested Design Procedures for Combined
Footings and Mats.
Suggested Design and Construction Procedures for
Pier Foundations.
Manual of Steel Construction (8th Edition).
Specifications for the Design of Cold-Form Steel
Structural Members with Commentary; American
Iron and Steel Institute (AJSI).
Structural Welding Code;
Society ( AWS).
American Welding
Reinforcing Steel Welding Code; AWS.
STRUCTURAL DESIGN CRITERIA
CLFI
SJI
UBC 1985
A-6
Commercial Standard for Industrial Aluminum and
Galvanjzed Steel Chain Link Fencing; Chain Link
Fence Institute {CLFI).
Standard Specifications and Load Tables; Steel
Joist Institute (SJI).
Uniform Building Code; International Conference
of Building Officials.
2.3 MISCELLANEOUS DOCUMENTS
SEAOC-80
R & M
Criteria
D & L
Criteria
Hydraulics
Dept. Design
Criteria
Geotechnical
Design
12-18-85
Recommended Lateral Force Requirements and
Commentary; Structural Engineers Association of
California, 1980 Edition.
Civil & Facilities Design Criteria, Bradley Lake
Project, R & M Consultants, Inc., Anchorage,
Alaska.
Transmission Facilities Design Criteria, Bradley
Lake Project, Dryden and LaRue, Inc.
"See criteria specific to structures in Part B"
Preliminary and Phase Geotechnical Design
Criteria Criteria
2-106-JJ
1-9-86 General Project Information and Civil Design
Criteria
STRUCTURAL DESIGN CRITERIA
A-7
3.0 MATERIALS
Materials listed below and conforming to the referenced ASTM
designation will be specified on the project. For specific design
requirements see Section 5. 0 Structural Design and Part B of this
criteria.
A. STEEL
Structural Steel
High-strength steels where
specified
Stainless Steel Plate
Stainless Steel Sheet
Penstock Steel
B. Bolts, Nuts, and Washers
2-106-JJ
High-strength for Permanent
Joints
High-strength Alloy for Joints
Unfinished Bolts
ASTM A36
ASTM A572, Grade 50
ASTM A167, Type 304 or
Type 316
ASTM A167, Type 304 or
Type 316
ASTM A710, Grade A,
Class 3
ASTM A325, Type 1,
(7/8 inch diameter)
ASTM A490, with yield
strength between 130 ksi
min and 145 ksi max,
(1 inch diameter)
ASTM A307, Grade B
STRUCTURAL DESIGN CRITERIA
c.
Corrosion-resistant Bolts, Nuts
and Washers for Removable
Structural Members
Crane Rail and Standard
Accessories
D. Steel Floor Grating and
Stair Treads
E. Roof and Floor Decking
F. Weld Filler Metal
G. Checkered Floor Plate
H. Pipe Handrail
I. Laduers
J. Safety Chain
K. Cement
2-106-JJ
A-8
ASTM A193, Grade B8 Bolts
ASTM A194, Grade 8 Nuts
Type A304 Washer
ASTM A759, No. 1 modified
rail, attached with
pressed clips and rever-
sible fillers for a tight
fit. Joint Bars ASTM A3
ASTM A569
ASTM A446 and coated with
zinc coating conforming
to ASTM A525
AWS D1.1 and Table 4.1.1
therein
ASTM A36 with a symmet-
rical raised diamond
pattern
1 1/2 in. IPS, Sch. 40, ASTM
A53, Grade B, or A500
Grade B, of comparable
section and strength
ASTM A36
ASTM A413, Class PC
Type II, low alkali
Portland Cement con-
forming to ASTM C150
STRUCTURAL DESIGN CRITERIA
A-9
L. Aggregates Coarse aggregates
conforming to ASTM C33
M. Reinforcing Steel ASTM A615, Grade 60
N. Welded Wire Fabric ASTM A185
0. Pipe and Floor Sleeves ASTM A53, Grade B,
or Penetrations Schedule 40 or ASTM A36
plate ma. terial
P. Prestressing Steels Later
2-106-JJ STRUCTURAL DESIGN CRITERIA
A-10
4.0 DESIGN LOADS
4.1 DEAD LOADS {D)
Dead loads consist of the weight of all permanent construc-
tion. Refer to Table 1 Selected Material Weights.
4.2 LIVE LOADS (L)
Live loads will consist of uniform surface loads or equiva-
lent point loads developed to represent loading effects due
to the movement of materials, equipment or personnel applied
on a temporary basis. Loads will be identified as live loads
when the item imposing the load is not permanent or rigidly
or permanently fixed to a structure. Live loads are assumed
to include adequate allowance for ordinary impact conditions.
Table 2 in Section 6.0 lists uniform floor loads to be used
in lieu of unavailable actual loads.
Uniform floor live loads may be omitted in regions where
actual equipment loads are provided and exceed the specified
floor loading.
Where equivalent uniform live, floor or point loads are used
to represent equipment, actual loads shall be checked against
assumed loads when information is available.
4.3 SNOW AND ICE LOADS (S.I)
2-106-JJ
For purposes of design, snow and ice loading will be consid-
ered to occur for a minimum of 6 months out of the year.
STRUCTURAL DESIGN CRITERIA
A-11
Snow loads as listed in Table 5 are developed for the project
based on the Department of the Army's technical document ETL
1110-3-317 and shall be used for buildings and structures:
Effects of removing half the snow from any portion of the
loaded area shall be investigated for all roofs. This
condition simulates loss of snow from a portion of roof due
to natural or man made causes.
The effects of ice loads on hydraulic structures as shown in
Part B of this Design Criteria shall be considered.
4.4 EQUIPMENT LOADS (M)
Selected equipment weights and estimated loads are listed in
Tables 3 and 4. Evaluate known equipment loads for empty
weight (dead weight of equipment), operating weight (full
contents)t and operational loadings (torquest etc.). Use
Table 2 load information when equipment information is not
available.
4.5 HYDRAULIC LOADS (H)
Hydrostatic and hydrodynamic loads are those imposed on
structures by water due to pressuret flow or earthquake.
Refer to the Hydraulic Design Criteria and to the
Geotechnical Design Criteria for specific loads.
4.6 SOIL AND ROCK LOADS
Refer to the Geotechnical Design Criteria for specific loads.
2-106-JJ STRUCTURAL DESIGN CRITERIA
A-12
4.7 WIND LOADS (W)
2-1 06-J ,)
Wind loads developed for the Bradley Lake project are based
on the 1985 UBC formula for wind pressure:
p :: C C q I e q s (UBC Chapt. 23, Eqn. 11-1)
Where:
p :: Design wind pressure
C :: Combined height, exposure and gust factor e
coefficient as given in UBC Table No. 23-G
C :: Pressure coefficient for the structure or portion q
of structure under consideration as given in UBC
Table No. 23-H
q
5
= Wind stagnation pressure at the standard height of
30 ft as set forth in UBC Table No. 23-F
I :: Importance factor as set forth in UBC Section
2311 (h).
For wind loads, refer to Tables 6 through 9, as applicable.
1. Wind Load Application:
Wind loads shall be applied orthogonally to buildings and
structures in only one direction at a time. For tanks or
structures supported on four legs in an elevated position
wind load shall be applied diagonally. Wind loads shall not
be combined with earthquake loadings; however, they shall be
applied in combination with snow loads.
STRUCTURAL DESIGN CRITERIA
4.8
4. 8. 1
A-13
2. Exposure Category and Importance Classification:
Wind pressures for the identified exposure condition of
Tables 6 through 9 shall be multiplied by the appropriate
importance factor developed for the project and listed in
Table 10.
SEISMIC LOADS (E)
General Seismic Conditions
Structures shall be subjected to seismic event loads in
accordance with the following basis of criticality:
Description
Non-Critical
Those structures which house
or support equipment or sys-
tems which,if damaged during
a major seismic event, could
be replaced or repaired within
one month or are not critical
to the continued operation of
the hydroelectric facility.
Critical
Those structures which house
or support equipment or systems
considered critical to the
continued operation of the
hydroelectric facility, and
which would take more than one
month to repair or replace or
would be prohibitive in cost to
repair or replace, if damaged
during a major seismic event.
Structure
All structures and equipment
supports not listed in
critical or hazardous
categories.
Main Dam Diversion Tunnel /
and Gate House
Power Tunnel including
Intake and Gate Shaft
I
J
Powerhouse and Appurtenances
Penstock and Spherical
Valves
Main Dam and Appurtenances
Spillway
Substation
J
2-106-JJ STRUCTURAL DESIGN CRITERIA
4.8.2
2-106-JJ
Hazardous
Those structur·es which house
or support equipment or systems
containing materials such as
acids, caustics, chemicals or
flammables which, if damaged,
could be hazardous to personnel,
the environment, or to the
continued operation of the hydro-
electric facility.
General Seismic Forces
A. Non-Critical Structures
1. Force Computation
A-14
Chemical Tanks
Fuel Tanks, Pumps
Caustic and Acid Tanks
Chlorine Systems
Non-critical structures shall be designed for effects of
seismic acceleration of 0.35g represented by:
Where:
V = 0.35 VI
V = Total lateral force or shear at base
W = Total dead load including
partition loads
2. Force Distribution
Distribution of forces shall follow UBC formula:
n
V:Ft+LFi
i = 1
(UBC Chapt. 23, Eqn. 12-5)
STRUCTURAL DESIGN CRITERIA
2-106-JJ
A-15
Where:
F t = 0. 07 TV (F t need not exceed 0. 25 V and may be
considered as zero where T = 0.7 sec, or less);
T = 0.05 h n (UBC Chapt. 23,
Eqn. 12-3A)
F. = Remaining portion of total base shear distributed
l
over the height of the structure including level n
according to UBC formula 12-7;
F (V-Ft) w h = X X X ....
L wi h. (UBC Chapt. 23,
l
i=1 Eqn. 12-7)
Where:
wi wx = That portion of W which is located at or is
assigned to level i or x, respectively;
h.h h = Height in feet above base to level i, n, or x,
1 n x
respectively.
Level n = That level which is upper most in the main
portion of the structure.
D = The dimension of the structure, in feet in a
direction parallel to applied force (not to be
confused with "D" used for dead load of
Section 4.1, herein).
STRUCTURAL DESIGN CRITERIA
2-106-JJ
A-16
3. Force Aoplications
Horizontal seismic forces shall be applied
orthogonally to rectangular structures.
Application of force shall be made in each
direction separately. \>!here tanks or towers are
elevated, application of seismic forces shall be
made diagonally and shall consider affects of
liquid movement. Seismic forces shall not be
applied concurrently with wind forces. Under
certain circumstances seismic forces shall consider
live load and effects of snow.
4. Vertical Forces
In addition to seismic effects due to horizontal
ground motion, structures shall be considered to
experience the effects of vertical seismic motion
equal to 2/3 the horizontal motion. Normal
application of this seismic force will consider the
horizontal and vertical forces to act separately.
B. Critical Structures
Development of seismic forces for critical structures
shall follow the re9ommendations set forth under Part B
of this Criteria. Items not identified under Part B,
but considered critical shall be designed for a static
force of:
v = 0.75 w
distributed in a manner similar to Section 4.8.2 (A.2),
and applied in accordance with item A.3. Vertical
forces shall be applied in accordance with Section 4.8.2
(A.4).
STRUCTURAL DESIGN CRITERIA
4.8.3
2-106-JJ
A-17
C. Hazardous Structure~
Structures for hazardous material shall be designed for
a static seismic force of:
v = 0.75 w
in a manner similar to Section 4.8.2, except that:
a. Spill containment barriers may be designed for a
static force of V = 0.35W with no increase in
allowable stresses.
b. Tanks or towers on elevated support legs shall be
designed to consider a static force of 0. 75W plus
the seismic effects of motion of the mass of liquid
contained '!'i thin the vessel. Calculation and
application of seismic induced forces shall follow
Chapter 11 of Navy document NAVFAC P-355, or
Chapter 6 of TID 7024 Nuclear Reactors and
Earthquakes.
Seismic Forces on Elements
Parts or portions of structures and nonstructural components
such as electrical fixtures or architectural items and their
anchorage to the main structural system shall be designed for
lateral forces in accordance with the following formula:
F = ZIC W x F.S. p p p
Where: F = Lateral forces on a part of the structures p
and in the direction under consideration;
STRUCTURAL DESIGN CRITERIA
A-18
I = 1.0 Importance Factor, unless otherwise
noted;
c = Numerical Coefficient as specified in p
Table No. 23-J;
z = 1.0 {UBC Zone 4);
W = Weight of object under consideration; p
UBC
F.S. = Factor of Safety to be applied as defined in
Part B. If item is not covered in Part B,
use F.S. = 1.0, except for hazardous
materials where F.S. = 2.0.
4.9 TSUNAMI AND SEICHE INDUCED FORCES
Refer to Part B for specific applications.
4.10 THERMAL LOADS (T)
2-106-JJ
Structures exposed to large temperature changes shall be
designed to consider the affect of induced stresses. Design
shall consider the following extreme exposure conditions:
Minimum Temperature -30°F
Maximum Temperature 85°F
Hodified temperature conditions may apply to enclosed
structures, and will be identified in Part B for specific
situations.
Change in length {see p. 6-7, AISC Manual) will be based on a
0 coefficient of expansion of 0.00065/100 F, for steel, and
0.00055/100°F, for concrete.
STRUCTURAL DESIGN CRITERIA
A-19
4.11 PIPE AND CABLE TRAY LOAD ALLOWANCES
2-106-JJ
Areas of heavily concentrated piping or cable tray runs shall
be designed for that increased loading. Where pipes or cable
trays are suspended from concrete, obtain the estimated
uniform or hanger loading from the Electrical and Power
Engineers.
A general load allowance shall be applied to the midspan of
all steel framing members to account for miscellaneous pipe
and cable tray loads, as follows:
Member
Girder
Stringer
12 in depth or less
2 kips
2 kips
The following shall apply:
Over 12 in depth
6 kips
3 kips
1. Design for the actual loads where information is
available.
2. Platform bracing angles, main brae ing, beams less than
W8, and channels shall not receive any load allowances
and shall not be hung with pipes or cable trays.
3. Load allowances shall not be added to the reactions at
girders or columns for the purposes of' designing
connecting members, however added load shall be used for
design of connections.
4. On vertical pipe runs where two hangers are used to
carry the load at a single clamp, the steel support
shall be designed to carry the full pipe load from
either hanger.
5. Where heavy pipe loads are hung from steel beams or
girders, the hanger prying action on the beam flange
shall be checked.
6. Applicable hydrostatic test loads shall be considered
for pipe supports or supporting structure.
STRUCTURAL DESIGN CRITERIA
A-20
4.12 ROOF TRUSS LOAD ALLOWANCE
Roof trusses shall be designed to allow for a 2 kip load
contingency at every second panel point applied at the lower
chord.
4.13 COLUMN LOAD ALLOWANCE
2-1 06-JJ
A. Vertical Allowance
For preliminary column sizing, a 15 kip load allowance shall
be applied to the tops of columns to take care of hung pipe,
ducts, miscellaneous equipment, and loads not yet defined.
Column loads shall be checked against actual loads.
Calculated reactions shall include thermal, pipe restraint,
wind, and earthquake forces as applicable. If the actual
loads exceed the known loads plus load allowance, the columns
shall be reanalyzed and, if necessary increased in size. The
column sizing need not be adjusted down in size unless loads
have been grossly overestimated.
B. Horizontal Support Allowance
Horizontal beams or trusses shall be used to prevent columns
from buckling. Horizontal struts shall be designed for an
axial load of not less than 1 0 kips or a percentage of the
actual column load, whichever is greater:
Support Column
Llr
140 max
141 to 200
Column Load Percentage
2
3
STRUCTURAL DESIGN CRITERIA
A-21
Where horizontal support trusses are used, the truss depth
should equal about one-tenth the span and the web system
members should be a minimum 3 1/2 in. by 3 in. by 5/16 in
double angles, or a T-section of similar properties.
Where wind· loads are carried by the same horizontal support
system, the framing shall be designed for either wind or
stability loading, whichever is largest, but the loads shall
not be additive.
4.14 BRACING LQAD
Bracing shall be designed for no less than a 10 kip axial
load.
4.15 TEMPORARY ROOF LQADS
When crane installation procedures require such, the framing
of the powerhouse roof shall be designed for loads from
lifting beams incorporated into the framing and used to hoist
the bridge crane into position. Live load on the roof may be
omit ted for this temporary condition of loading, and the
working stresses for the steel roof members may be increased
33 percent.
Roof member sizes may be increased to suit temporary use in
lifting heavy equipment. Such members would become part of
the roof framing. For temporary conditions, a one-third
increase in working stresses will be allowed.
4.16 CRANE IMPACT ALLOWANCE
2-106-JJ
Powerhouse cranes have relatively low hoisting speeds and DC
controls, which provide for more precise handling. Values to
be used for impact and horizontal forces for the powerhouse
crane shall be as follows:
STRUCTURAL DESIGN CRITERIA
Rated Load,
Tons
150
*Impact
%
10
**Lateral
Force. %
10
* Based on maximum wheel loads
A-22
***Longitudinal
force. %
10
** Based on rated loads plus trolley weight applied at top
of crane rail, half on each side.
••• Based on maximum wheel loads applied at top of rail.
Impact and horizontal forces shall be included in the design
of columns but not footings. Side thrust and impact shall
not be considered simultaneously.
Neither earthquake nor wind loads shall be considered acting
simultaneously with crane live loads in designing columns and
foundations. full wind or seismic shall be considered acting
with crane dead load.
4.17 HOIST TROLLEY LOADS
Supports for hoist monorails shall be designed to include the
trolley, hoist, and monorail loads, and any pipe loads.
Impact for motor-operated hoists shall be 25 percent of the
lifting capacity added to the hoist and trolley load.
4.18 TRUCK. FORK LIFT. AND CART LOADS
2-106-JJ
Where truck entrances are provided, the floor area of the
trucking aisle shall be designed, as a minimum, for 350 psf
or an HS20 truck loading plus 10 percent impact, whichever
governs. fork lift aisles shall be designed to accommodate
selected wheel loads.
Refer to Table 2, for uniform cover and hatch loads.
STRUCTURAL DESIGN CRITERIA
A-23
4.19 VIBRATIONAL LOADS
It is assumed that most equipment will be properly bedded and
anchored or isolated so as to preclude the possibility of
vibration induced loads being imposed on structures, however,
consult the Lead Structural Engineer regarding application of
dynamic loads due to vibrating equipment.
4.20 CONSTRUCTION LQADS
2-106-JJ
A 25 psf live load shall be added to all floor construction
loads to account for men and equipment during construction.
The Responsible Project Construction Specialist may require
that additional forces be considered.
STRUCTURAL DESIGN CRITERIA
A-24
5.0 STRUCTURAL DESIGN
5. 1 LOAD COMBINA TIQNS
2-106-JJ
Load combinations for specific structures will be identified
in Part B of this document. Should an area not be identi-
fied, and in the absence of other instructions, the following
loading combinations will be observed:
A. For Dead Load, Live Load, Wind and Seismic
D + L
D + L + W
D + L + E
D + L + S
D + L + W + 0.50S
D + L + 0.50W + S
D + L + E + 0.50S
A 1/3 stress increase in stresses may be allowed
for combinations including wind per the applicable
codes; allowable stresses for seismic conditions
shall be as defined herein.
B. For Eguipmeot Supports
M (empty) + W or E
M (operating) + L
M (operating) + L + (W or E)
M (flooded or testing load)
The engineer responsible for design of a structure
shall identify the critical load combinations.
STRUCTURAL DESIGN CRITERIA
A-25
5.2 STABILITY REQUIREMENTS
2-106-JJ
Specific conditions for individual structures are elaborated
in Part 8 of the criteria, however all structures shall be
checked for the safety factors as described below.
A. Overturning
The factor of safety against overturning shall be at
least 1.5.
B. Sliding
The factor of safety against sliding shall be at least
1.5. The coefficient of friction shall be obtained from
the Responsible Geotechnical Engineer. Passive pressure
shall not be used to resist horizontal forces unless
specifically allowed by the Responsible Geotechnical
Engineer.
C. Flotation
The factor of safety against flotation shall be at least
1 . 1 under the "construction" condition and 1. 5 under
"completed" condition. The stabilizing force shall be
the dead weight of the structure alone. Live load shall
not be considered as assisting resistance.
D. Anchoring Structure
Structural anchorage to rock or foundation may be used
to resist forces tending to upset the stability of a
structure. Type of anchorage system shall be determined
on a case-by-case basis. Refer to Part B of this
criteria.
STRUCTURAL DESIGN CRITERIA
A-26
5.3 STEEL DESIGN
2-106-JJ
Connections
Field connections with high strength bolts shall be bearing
type connections, except for members having reversible wind
or seismic stresses where friction type joints shall be
required. Connections shall be designed to effectively
include the prying action forces where applicable.
Bolted connections of structural steel members shall be made
with 7/8 in. diameter ASTM A325 Type 1, Class E, high
strength bolts. A 1 in. diameter ASTM A490 high strength
bolts may be used where allowed by the Lead Structural
Engineer.
Unless other reactions are shown or connections detailed on
the drawings, the following minimum connections are specified
for fabricator's use. Review shop drawings to ascertain that
these minimums are provided.
Beam
Depth
Inches
36
33
30
27, 24
21
18
16
14, 12
10, 8
7 and under
Number of Bolts in
Outstanding Legs of
Connection Angle
20 = 10 rows
18 = 9 rows
16 = 8 rows
14 = 7 rows
12 = 6 rows
10 = 5 rows
8 = 4 rows
6 = 3 rows
4 = 2 rows
2 = row
The minimum connection allowed for horizontal bracing members
shall be a 2 bolt connection in double shear, or a 4 bolt
connection when using shear tabs.
STRUCTURAL DESIGN CRITERIA
2-106-JJ
A-27
Stairways and girts shall use 3/4 in. diartteter ASTM A307
bolts.
Attachments for removable beams and equipment, or where
corrosion is of concern, shall use stainless steel ASTM A193,
Grade B8 bolts, ASTM A194, Grade 8 nuts, and ASTM A304
washers.
For exterior stairs galvanized stair treads 10 in. deep x 1
in. (minimum) thick x 44 inches wide will be used. Minimum
size stringer allowed shall be C9x13.4. Concrete filled pan
type treads will be used within buildings.
Grating for floor areas, walkways and hatches shall be
galvanized and shall have as a minimum 1-1/4 in. deep x 3/16
inch thick bearing bars spaced at 1-3/16 in. Actual depth
shall be controlled by design load and span.
Handrail. Guardrail. and Kickplates
Handrail shall be nominal 1-1/2 in. diameter, Schedule 40,
ASTM A53, Grade B pipe. Post spacing shall not be greater
than 8 ft with a top, bottom and center rail provided.
Guardrail shall be nominal 2 in. diameter, Schedule 40, ASTM
A53, Grade B pipe and will otherwise meet the handrail
requirements. Pipe handrail and guardrail connections will
be of welded construction.
Four-inch high kick plates shall be provided around all clear
openings greater than 1 in. and along standard handrails.
Checkered Plate
Checkered plate shall be a minimum 5/16 in, thick, ASTM A36
carbon steel with a symmetrical raised diamond pattern on the
walking surface.
STRUCTURAL DESIGN CRITERIA
2-106-JJ
A-28
Steel Floor Forms and Roof Deck
Steel floor forms shall be a minimum 1-1/2 in. deep, 20 gauge
roll formed corrugated metal deck, QL-UKX type as
manufactured by H.H. Robertson Co., Pittsburgh, PA, or equal.
As a minimum steel roof deck shall be a minimum 3 in. deep,
20 gauge roll formed metal Q-deck, QL-style as manufactured
by H.H. Robertson, or equal. Should slope of roof be
adjusted to reduce load, gauge may be reduced to 22 gauge, if
warranted.
Steel floor forms and roof decks shall be attached to
supporting framing by welding with minimum 3/4 in. diameter
fusion welds (puddle), or by use of approved power actuated
fasteners.
Crane Rails and Stops
Size, weight and shape of crane rails and accessories shall
be per the AISC Manual, based on the rail size specified by
the crane manufacturer. Type of crane stops shall meet the
crane manufacturer's recommendations.
Welding Materials
Filler material for welding shall conform to AWS D1. 1 and
Table 4.1.1 therein. In general, E70XX Welding electrodes
shall be used. Special welding electrodes as may be required
for the penstock and steel liners shall be identified in Part
B.
Deflections
Deflections shall not exceed the following deflection
limitation ratios multiplied by the span length:
STRUCTURAL DESIGN CRITERIA
Member Type or Item
1.
2.
3.
4.
5.
6.
7.
8.
g.
10.
11.
12.
Primary Structural
Framing member
Secondary Structural
Framing member (Purlins,
girts, etc.)
Exterior Wall and Roof
panels
Metal floor form with
concrete slabs
Grating
Checkered floorplate
Steel Decking
Roof Joist (per SJI)
Floor Joists (per SJI)
Monorails
Crane Girders
Lateral Deflections
Minimum Member Sizes
A-29
Deflection
Limitation
1/240 (maximum)
1/180 (maximum)
1/180 (maximum)
1/360 (maximum)
1/4 in. for 100
psf live load
1/100 (live load)
1/240 (total load)
1/360 (maximum)
1/360 (maximum)
1/500 (maximum)
1/1200 (maximum)
1/400 (maximum)
Minimum member sizes allowed shall be based on the following:
Minimum Dimensions (in.)
Flange Flange Member or Web
Member Type Width Thickness Leg Depth Thickness
Wide Flange, 4 1/4 6 1/4
s and M Shapes
Channels 2 1/4 6 3/16
Angles 2 1/4 2 1/4
"S" shapes shall be used for monorails.
2-106-JJ STRUCTURAL DESIGN CRITERIA
2-106-JJ
A-30
Special Material Considerations
Design of structural steel members due to fatigue induced by
vibration shall follow the recommendations of the AISC
Specification S326.
Where cold temperature conditions must be considered, the
durability of structural steel will be controlled by the
metallurgy of the material. For special conditions, consult
with the Materials Specialist. Also fatigue considerations
involving cold temperatures shall be addressed by the
Materials Specialist.
Drilled Concrete Anchor Bolts
Drilled concrete anchor bolts shall
Kwik-Bolts as manufactured by Hilti
Undercut Anchors as manufactured
Engineering Corp., or equal.
Rock Anchors
be Stainless Steel
Inc. or Williams
by Williams Form
Rock anchors or rock bolt assemblies shall be Dywidag
Threadbar as manufactured by Dywidag Systems International
or equal, meeting the approval of the Responsible
Geotechnical Engineer.
Studs and Threaded Anchors
Studs and threaded anchors used in attaching plates, etc. to
concrete shall be as manufactured by Nelson Stud Welding
Co., or equal.
STRUCTURAL DESIGN CRITERIA
2-106-JJ
A-31
Waters tops
In general, waterstops shall be natural rubber, synthetic
rubber, or polyvinyl chloride, as manufactured by W.R.
Meadows, Inc., W.R. Grace & Co., or equal. Waterstops shall
be dumbbell or center-bulb dumbbell types 6 in. or 9 in.
thickness as design dictates. Waters tops in vertical or
horizontal construction, control, or expansion joints shall
be capable of resisting the maximum pressures and movements
anticipated. Split-type, cellular-type, or baffle type
wa terstops with a minimum 1/8 in. thickness, shall not be
used. Flat metal waterstops shall be used in horizontal
construction joints. Waterstops for the dam or other
special areas shall be addressed in Part B within the
appropriate section.
Conduit
Conduit shall be as identified on the drawings.
or aluminized conduit or fittings shall be
embedment in concrete.
Sleeves
No aluminum
allowed for
Anchor bolt sleeves shall be used for anchor bolts, up to
and including 3 inch diameter. Unless proximity to edge of
concrete dictates use of steel pipe sleeves, plastic sleeves
are preferred and may be Wilson Anchor Bolt Sleeves, or
equal.
Steel pipe sleeves and floor sleeves shall be fabricated
from ASTM A53, Grade B, Schedule 40 pipe material and ASTM
A36 plate material.
STRUCTURAL DESIGN CRITERIA
A-32
5.4 CONCRETE DESIGN
2-106-JJ
A. General
Concrete structures shall be designed in accordance
with ACI 318-83. Ultimate Strength Design procedures
should be used, unless directed otherwise.
Generally, load combinations follow the recommendations
of ACI 318-83, Chapter 9. Special load combinations
identified in Part B shall be used where applicable.
The seismic provisions of ACI 318, Appendix A shall be
considered in the design, where feasible.
B. Concrete Strength
The minimum specified compressive strength to be used
for design shall be as identified in Part B for specif-
ic structures. Where Part B does not apply, a minimum
specified 28 day compressive strength of 4,000 psi
shall be used for purposes of design.
C. Reinforcement
Deformed reinforcing bars having a yield strength ( f ) y
of 60 ksi shall be used. In addition, the following
shall be observed:
1. Minimum ties shall be No. 4 rebar.
2. All isolated circular or square columns shall
be spirally reinforced.
3. Minimum reinforcing allowed shall be No. 4.
Try to keep rebar sizes below No. 11's.
4. Lengths should be kept to 40 feet maximum.
5. The number of different sizes of reinforcing
bars used should be kept to a minimum. Use
class C lap splices.
STRUCTURAL DESIGN CRITERIA
A-33
D. Metal floor deck used as floor forms must be checked
for load and span limitations. Keep span within deck
manufacturer's recommended limitations wherever possi-
ble.
E. Foundation depths may be effected due to frost. Depths
of foundations shall be reviewed by the Responsible
Geotechnical Engineer before design proceeds. Siting
conditions may dictate the requirements for special
insulation procedures.
5.5 MASONRY DESIGN
2-106-JJ
Masonry construction shall not be used unless directed
otherwise by the Lead Structural Engineer.
STRUCTURAL DESIGN CRITERIA
6.0
2-108-JJ
TABLES AND FIGURES
TABLE 1
SELECTED MATERI~L WEIGHTS
(lbs/ft )
(Soil and rock loads must be verified)
Mass Concrete
Reinforced Concrete
Steel
Water
Ice
Sea Water
Rock
*Silt -Vertical
-Horizontal
*Backfill
-Dry
-Saturated
-Submerged
*Applicable for Phase I work,
will be expanded for Phase II work.
11! 5
150
1190
62 .1!
56
64
170
120
85
120
135
75
A-34
STRUCTURAL DESIGN CRITERIA
A-35
TABLE 2*
MINIMUM LIVE LOADS FOR FLOORS AND DECKS
Area Description Approx, Floor El. Live Load Remarks
Powerhouse
Generator Floor
Service Bay Floor
Equipment Floor
Tailrace Deck
Valve Pit Area
Runner Gallery
Control Room
HVAC Room
Hatch Covers and Grating:
Generator Floor
Turbine Floor
Others
General-Buildings
Meeting areas, lunch rooms,
locker facilities, office
areas
Stairs and corridors
Storage Areas, Heavy
Storage Areas, Light
Machine Shop
(ft) (psf)
42
42
21
21
8
5
42
60
300
800
300
150
300
300
250
250
300
300
100
100
250
125
250
Check maximum
equipment
loads.
Use loaded vehicle
wheel loads. Assume
load is either 1/2
stator ring or full
generator rotor assy.
w/o coupling shaft.
Minimum HS20-44
wheel load.
Check maximum
gate laydown
load.
On rock.
On rock.
Check maximum
equipment load.
Same as adjacent
floor load.
• Live loads may not be reduced in accordance with UBC procedures
without prior approval of the Lead Structural Engineer.
2-108-JJ STRUCTURAL DESIGN CRITERIA
TABLE 3
ESTIMATED EQUIPMENT WEIGHTS
(Subject to verification)
Equipment Tvoe
Turbine
Total Weight
Scroll Case Manifold
Housing
Rotating Parts
Generator
Runner
Shaft
Total Weight
Heaviest Lift (rotor with poles)
Rotor without shaft
Shaft, plus lower bracket
Stator, one half
Thrust Bearings (no oil)
Bearing Bracket (less bearing)
Transformer 115 kV
Core and Coils
Tank and Fittings
Transformer with oil
Weight of oil
Shipping weight
A-36
Estimated Weight
345,000 lbs.
150,000 lbs.
75,000 lbs.
29,000 lbs.
25,000 lbs.
450,000 lbs.
290,000 lbs.
21W, 000 lbs.
75,000 lbs.
75,000 lbs.
20,000 lbs.
35,000 lbs.
100,000 lbs.
50,000 lbs.
200,000 lbs.
50,000 lbs.
150,000 lbs.
2-108-JJ STRUCTURAL DESIGN CRITERIA
Eauipment Type
Spherical Valve
TABLE 3 (Continued)
Estimated EquiPment Weights
(Subjecc to verification)
Valve rotor and Trunnion
(heaviest part to be handled)
Valve (half body)
Total valve assembly
Tailrace gate
Bridge Crane
Main hook capacity
Auxiliary hook capacity
Total crane weight
Bridge weight
Trolly weight
Tail race hoist
Weight
Capacity (estimated)
Miscellaneous Hoists
2 ton
5 ton
10 ton
A-37
Estimated Weight
50,000 lbs.
20,000 lbs.
85,000 lbs.
12,000 lbs.
150 ton
25 ton
165,000 lbs.
90,000 lbs.
75,000 lbs.
3,000 lbs.
25 ton
500 lbs.
1,000 lbs.
1,500 lbs.
2-108-JJ STRUCTURAL DESIGN CRITERIA
Equipment Type
Turbine
TABLE 4
MISCELLANEOUS EQUIPMENT LOADS
(Subject to verification)
Maximum hydraulic thrust (momentary) vertical
down
Load on thrust bearing
Maximum lateral thrust from non-symmetric
loading
Generator
Short circuit torque
Bridge Crane
Maximum wheel load per wheel
TABLE 5
SNOW LOADS
Ground Snow Load
Powerhouse Roof
Powerhouse Tailrace Deck
Other Building Roofs
and Covered Structures
Other Building Lower Roofs
(potential drifting)
60 psf
85 psf
110 psf
85 psf
110 psf
A-38
Estimated Load
2,000 lbs.
380,000 lbs.
70,000 lbs.
(later)
100,000 lbs.
2-108-JJ STRUCTURAL DESIGN CRITERIA
El. Above
Grade (ft)
0-20
20-40
40-60
60-100
100-150
TABLE 6
WIND PRESSURES* (SPEED V = 100 MPH)
I = 1.0 1 EXPOSURE B, PRESSURE (psf)
A-39
CONDITION 1 -OVERALL STRUCTURE (Area > 1,000 sf)
Windward
+15
+17
+21
+23
+27
Leeward
-09
-10
-13
-14
-17
Leeward
Flat
-13
-15
-18
-20
-24
Roof
Windward
Slope 9:12
-13
-15
-18
-20
-24
CONDITION 2 -STRUCTURAL ELEMENTS (Area ~ 1 '000 sf)
R of
End
Ridges/
Eave
El. Above EnclQseg Blgg. Wall Eave Corners
Grade {ft) Pressure Suction Parapets Corners InteriQr Overhang
0-20 +22 -20 24 -36 -20 -51 -55
20-40 +25 -23 27 -42 -23 -58 -63
40-60 +31 -29 34 -52 -29 -73 -78
60-100 +34 -32 37 -57 -32 -80 -86
100-150 +41 -37 44 -68 -37 -95 -101
CONDITION 3 -ISOLATED OBJECTS & MISC. STRUCTURES
Interior
Ridges/
Eaves
W/0
Oyer hang
-36
-42
-52
-57
-68
El. Above Iank§ ana S2lia IQH~C§ Open Frame Signs, Pole and
Grade (ft) Sg/Rect Hex/Oct Round/Elliot. TQ)lers Minor Structures
0-20 26 20 15 36 26
20-40 29 23 17 42 29
40-60 36 29 21 52 36
60-100 40 32 23 57 40
100-150 47 37 27 68 47
*See Notes for Tables 6 through 9
2-108-JJ STRUCTURAL DESIGN CRITERIA
El. Above
Grade (ft)
0-20
20-40
40-60
60-100
100-150
A-40
TABLE 7
WIND PRESSURES* (SPEED V 100 MPH)
I = 1.0, EXPOSURE C, PRESSURE (psf)
CONDITION 1 -OVERALL STRUCTURE (Area> 1.000 sf)
Windward Leeward Roof
Leeward Windward
+25
+27
+31
+33
+37
-16
-17
-20
-21
-23
Flat Slope 9: 12
-22 -22
-24 -24
-27 -27
-29 -29
-33 -33
CONDITION 2 -STRUCTURAL ELEMENTS {Area ~ 1.000 sf)
RQof
End
Ridges/
Eave
El. Above Em~J.Qseg Blgg. Wall Eave Corners
Grad (ft) Pressure SuctiQn Parapets Corners InteriQr Overhang
0-20 +37 -34 41 -62 -34 -87 -94
20-40 +41 -37 44 -68 -37 -95 -101
40-60 +47 -43 51 -78 -43 -109 -117
60-100 +50 -46 54 -83 -46 -117 -125
100-150 +56 -52 61 -94 -52 -131 -140
CONDITION 3 -ISOLATED OBJECTS & MISC. STRUCTURES
Interior
Ridges,
Eaves
W/0
Over haw
-62
-68
-78
-83
-94
El. Above
Grade (ft)
Tanks ang SQlid TQwers
Sg/Rect Hex/Oct Roung/Ellipt.
Open Frame
Towers
Signs, Pole and
MinQr Structures
0-20
20-40
40-60
60-100
100-150
44
47
55
58
66
34
37
43
46
52
*See Notes for Tables 6 through 9
2-108-JJ
25
27
31
33
37
62
68
78
83
94
STRUCTURAL DESIGN CRITERIA
44
47
55
58
66
El. Above
Grade (ft)
0-20
20-40
40-60
60-100
100-150
A-41
TABLE 8
WIND PRESSURES* (SPEED V : 120 MPH)
I= 1.0, EXPOSURE B, PRESSURE (psf)
CONDITION -OVERALL STRUCTURE (Area > l,OOOsf)
Windward
+21
+24
+30
+33
+39
Leeward
-13
-15
-18
-20
-24
Leeward
Flat
-18
-21
-26
-29
-34
Roof
Windward
Slope 9:12
-18
-21
-26
-29
-34
CONDITION 2-STRUCTURAL ELEMENTS (Area~ 1.000 sf)
fig of
End
Ridges/
Eave
El. Above Em~lQsed Blgg. Wall Eave Corners
Grage (ft) Pressure SuctiQn Parapets Corners Interior Oyer hang
0-20 +31 -29 34 -52 -29 -73 -78
20-40 +36 -33 39 -59 -33 -83 -89
40-60 +44 -41 48 -74 -41 -104 -111
60-100 +49 -45 53 -82 -45 -114 -122
100-150 +58 -53 63 -96 -53 -135 -144
CONDITION 3 -ISOLATED OBJECTS & MISC. STRUCTURES
Interior
Ridges/
Eaves
Oyer hang
-52
-59
-74
-82
-96
El. Above
Grage (ft)
Tanks and SQlig Towers
Sq/Rect Hex/Oct RQung/Ellipt.
Open Frame
Teyers
Signs, Pole and
Minor Structures
0-20
20-40
40-60
60-100
100-150
36
41
52
57
67
29
33
41
45
53
*See Notes for Tables 6 through 9
2-108-JJ
21
24
30
33
39
52
59
74
82
96
STRUCTURAL DESIGN CRITERIA
36
41
52
57
67
El. Above
Grade (ft)
0-20
20-40
40-60
60-100
100-150
A-42
TABLE 9
WIND PRESSURES* (SPEED V = 120 MPH)
I = 1.0, EXPOSURE C, PRESSURE (psf)
CONDITION 1 -OVERALL STRUCTURE (Area > J,OOOsf)
Windward Leeward Roof
Leeward Windward
+36
+39
+44
+47
+53
-22
-24
-28
-30
-33
Flat Slope 9;12
-31 -31
-34 -34
-39 -39
-41 -41
-47 -47
CONDITION 2 -STRUCTURAL ELEMENTS (Area ~ 1,000 sf)
BQof
End Interio
Ridges/ Ridges,
Eave Eaves
El. Above EnQJ.Qsed BJ.gg. Wall Eave Corners
Grade (ft) Pressure Suction Parapets Corners InteriQr Overhang Oyer han
0-20 +53 -49 58 -89 -49 -124 -133 -89
20-40 +58 -53 63 -96 -53 -135 -144 -96
40-60 +67 -61 72 -111 -61 -155 -166 -111
60-100 +71 -65 77 -118 -65 -166 -178 -118
100-150 +80 -73 87 -133 -73 -187 -200 -133
CONDITION 3 -ISOLATED OBJECTS & MISC. STRUCTURES
El. Above Ienks an!l ~Qlig IQHers Open Frame Signs, Pole and
Grage (ft) Sq/Rect Hex/Oct Round/Ellipt. TQHers MinQr Structure~
0-20 62 49 36 89 62
20-40 67 53 39 96 67
40-60 78 61 44 111 78
60-100 83 65 47 118 83
100-150 93 73 53 133 93
*See Notes for Tables 6 through 9
2-108-JJ STRUCTURAL DESIGN CRITERIA
A-43
TABLE 10
WIND LOAD IMPORTANCE FACTOR
Main Dam Diversion Outlet
Structures
Main Dam Diversion Gate House
Main Dam Structures
Powerhouse and Attached
Facilities
Substation
Nuka Diversion Structures
Middle Fork Diversion
Structures
Miscellaneous Structures
Exposed Coastal Facilities
Exoosure
B
c
c
Average
of B+C
Average
of B+C
B
B
B*
c
*Consult the Lead Structural Engineer.
2-108-JJ
Importance
Factor
1.0
1.15
1. 15
1.15
1. 15
1. 0
1.0
1.0*
1. 15
Design
Wind
Sneed (moh)
120
120
120
100
100
120
120
100
100
STRUCTURAL DESIGN CRITERIA
NOTES FOR TABLES 6 THROUGH 9
1. (+) Indicates a load directed inward.
(-) Indicates a load directed outward.
{ ) No sign indicates load may be applied in any direction.
A-44
2. A structure with more than 30 percent of any one side open shall
be considered an open structure. See Lead Structural Engineer
for wind pressures on open structures.
3. Local pressures shall apply over a distance from the discontinui-
ty of 10 feet or 0.1 times the least width of the structure,
whichever is smaller.
4. Wind forces on cladding connections shall be calculated
multiplying the tabulated loads by a factor of 1.5.
by
5. Local pressures on structural elements, walls and roofs may be
considered simultaneously, but not in combination with overall
structure loads.
6. Local wall and roof pressures shall not be used when computing
entire bent, structural frame, or moment stability of structure.
7. For categories not listed in the tables, consult the Lead
Structural Engineer.
2-108-JJ STRUCTURAL DESIGN CRITERIA
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
2-108-JJ
PART B
SPECIAL REQUIREMENTS AND DESIGN CRITERIA
FOR MAJOR STRUCTURES
MAIN DAM DIVERSION
MAIN DAM
SPILLWAY
POWER TUNNEL AND GATE SHAFT
PENSTOCK
POWERHOUSE
TAILRACE
SUBSTATION AND TRANSMISSION SYSTEM
MIDDLE FORK AND NUKA DIVERSIONS
COFFERDAMS
A-45
STRUCTURAL DESIGN CRITERIA
ALASKA POWER AUTHORITY
BP~DLEY LAKE HYDROELECTRIC PROJECT
J.O. 15500
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
PART B, SECTION 1.0
REVISION: 0
DATE: JANUARY 23, 1986
STONE & WEBSTER ENGINEERING CORPORATION
ANCHORAGE, ALASKA
B-1-1
1.0 MAIN DAM DIVERSION
1.1 FUNCTIONAL DESCRIPTION
?_ 1 n'7 __ y .T
Bradley Lake flows need to be diverted or passed downstream
to allow for construction of the main dam and other associ-
ated structures located within the river channel near the
lake outlet. The lake water level will be lowered
approximately 10 feet below the existing natural level when
flows are diverted through the diversion tunnel.
The water level of the completed reservoir may require
lowering for purposes of safety inspection and possible
repair such as after a significant seismic event. Further,
controllable low flow releases of water for fish needs in
the Lower Bradley River must be available downstream of the
dam during construction and during regular plant operation.
To accomplish these tasks a short diversion tunnel will be
constructed through the right abutment of the dam. The
tunnel will consist of an inlet works, the diversion tunnel
(about 400 feet long), and the outlet works.
The inlet works, located at the upstream end of the tunnel,
will be comprised of bulkhead gates and a concrete structure
to support the gate guides and to form a transition in cross
section to the shape of the lined tunnel. The first half of
the tunnel, upstream of the control gates, will be
concrete lined while the second half of the tunnel
downstream of the gates will include a steel penstock 10'-6"
diameter. A rock plug will be temporarily left in place
upstream of the intake structure to act as a cofferdam
during construction. Two fish water intakes will be
embedded in the invert of the diversion tunnel. The
bulkhead gates may be used, should trash plug the tunnel,
for temporary cleanout purposes in addition to emergency or
inspection situations.
(
1. 2
1.2.1
2-107-JJ
B-1-2
The tunnel itself will be a modified horseshoe shaped,
concrete lined tunnel cut through rock. Two 26-inch diame-
ter pipes will be embedded in the corners of the tunnel for
the full length.
The outlet works will consist of a concrete outlet portal
structure and a concrete apron. The two fish water pipes
will discharge onto an outlet portal apron.
Flow through the diversion tunnel and consequently the water
level within the Bradley Lake Reservoir will be controlled
by a hydraulically operated gate. The control gate and a
guard gate will be located midway along the diversion
tunnel, in a vertical gate shaft. The tunnel will constrict
at the location of the gates. The shaft will be concrete
lined and covered with a gate house structure, and will be
provided with access stairs and mechanical or hydraulic
equipment for control and removal of the gates.
ENGINEERING/DESIGN CONSIDERATIONS
Construction Considerations
Construction of the main dam diversion tunnel will be
accomplished in two phases. The first phase will be accom-
plished using a temporary concrete hatching facility.
During the second phase of construction, the access roads
and construction facilities, including a site concrete
batching plant, will be operational. Due to the remoteness
of the site and shipping and transportation limitations,
material quality and weight savings will be a prime
consideration when designing the main dam diversion.
STRUCTURAL DESIGN CRITERIA
2-107-JJ
B-1-3
The two phases of construction are identified below:
Phase I:
a. Cut upstream and downstream tunnel portals. Leave
temporary rock plug in place approximately 30 feet
upstream of the entry portal. Temporary plug to act as
a cofferdam with top of rock at elevation 1090± feet;
b. Excavate tunnel (by drill and blast);
c. Construct intake structure including gate guide embed-
ments;
d. Install fish water intakes and 26-inch diameter pipes
up to Phase I limit;
e. Remove rock plug from in front of intake portal;
f. Allow lake level to reach equilibrium until construc-
tion of the dam and appurtenant structures are com-
plete;
g. Install bulkhead gates temporarily, if required, to
clean trash from the tunnel.
Phase II:
a. Install bulkhead gates at intake portal of diversion
tunnel;
b. Install remaining 26-inch diameter fish water release
lines to end of tunnel and connect to Phase I lines;
c. Open fish water release lines;
d. Excavate gate shaft;
e. Complete rock grouting and rock bolting as required;
f. Line upstream section of tunnel and gate shaft with
concrete, install steel penstock in tunnel downstream
of gates, and construct outlet portal structure;
g.
h.
i.
Construct gate structure, and gate control house;
Install and test control and guard gates;
Close gates, flood tunnel, and remove bulkhead gates by
barge.
STRUCTURAL DESIGN CRITERIA
(
1.2.2
B-1-4
Special pesign Considerations
Design and construction of the diversion tunnel is critical
to the construction of the dam and appropriate support
structures. Once completely installed, it must remain
operational to control water levels and to provide a means
of lowering the lake reservoir during safety inspections and
repair activities.
Equipment associated with the diversion tunnel including the
gates and valves must remain functional over the full range
of weather and loading conditions anticipated, including
major seismic events.
Weephole arrangement -later
1.3 SUPPLEMENTAL DESIGN CRITERIA
1. 3. 1
2-107-JJ
General
General design criteria as established in Part A -General
Structural Design Criteria will apply unless otherwise noted
or as supplemented herein. For supplemental information,
see the Hydraulic and Geotechnical Design Criteria.
Materials
The following materials will be used:
A. Concrete
Concrete with a minimum specified compressive strength
of 4,000 psi at 28 days shall be used.
STRUCTURAL DESIGN CRITERIA
)
)
2-107-JJ
B-1-5
B. Shotcrete
See Geotechnical Design Criteria
C. Reinforcing Steel
ASTM A615, Grade 60
D. Structural Steels
a. Gate Guides -ASTM A36 guide plates and ASTM A167
Type 316 stainless steel bearing plates
b. Bulkhead Gates -ASTM A572
c. Control and Service Gates -By vendor
d. Penstock -ASTM ..A3'6'"" steel
E. Fish Water Pipe
'-"To 'Q e .:: h.1o"'q ..o. d ...--:,:: A. 1 1 0
"'
Steel pipe with couplings and holddown anchors at
intermediate points along lines.
F. Rock Bolts and Dowels
See Geotechnical Design Criteria.
G. Grouts
Grouts used for injection grouting of rock formations
shall follow the requirements of the Geotechnical
Design Criteria.
Grouts used for bedding of structural elements embedded
in the concrete structures shall follow the Concrete
Specialist requirements for grouts exposed to high
pressure conditions.
STRUCTURAL DESIGN CRITERIA
1. 3. 3
2-107-JJ
B-1-6
H. Coating Systems
1. Tunnel Liner-unsealed,
2. Inlet/Outlet Portal Concrete Structure -unsealed,
3. Bulkhead Gates -two coats coal tar epoxy,
4. Bulkhead Gate Guides -coal tar epoxy on ASTM A36
material,
5. Control and Service Gates -inorganic zinc prime
coat with two coats of coal tar epoxy overcoat,
6. Control and Service Guides and Gate Frames
inorganic zinc prime coat with two coats of coal
tar epoxy overcoat,
1. Fish Water Intake lines -not coated.
Design Loads and Load Combinations
Loads
A. General Loads
1. Dead Loads,
2. Rock Loads -Static loads,
3. Hydrostatic Load -External -Tunnel unwatered
with bulkhead gates in place, PMF condition,
4. Hydrostatic Load: -Internal -Tunnel filled to
control gate, PMF condition,
5. Hydrodynamic Load -Control gate operation,
6. Earthquake Load -Horizontal,
1. Earthquake Load -Vertical,
8. Hydrodynamic Load -Earthquake acceleration with
normal maximum headwater elevation,
9. Hoisting Forces -Loads applied while removing
or operating gates,
STRUCTURAL DESIGN CRITERIA
2-107-JJ
B.
B-1-7
10. Construction Loads -Additional loads or construc-
tion conditions, applied or anticipated during
construction efforts or imposed during maintenance
operations,
11. Ice Loading,
12. Snow Loading,
13. Wind Loading,
14. Live Loading.
Hydraulic and Rock Loads will be obtained from the
Responsible Hydraulic or Geotechnical Engineer and as
stated below. (Designs shall not consider impact loads
due to objects hitting structures or blast loads, which
are considered negligible.)
RoQk J..Qads
See the Geotechnical Design Criteria.
C. Hydrostatic Pressures
Hydrostatic loads will be based on the high water
elevation at Probable Maximum Flood ( PMF), elevation
1191 feet, except under earthquake conditions where
hydrostatic 'loads will be based on normal maximum
headwater level, elevation 1180 feet. See profile of
piezometric information over length of diversion struc-
ture provided in the Geotechnical Design Criteria.
D. Hydrodynamic J..Qads
Loads imposed on the diversion structure and its parts
due to flowing water will be considered in combination
w1 th rock and hydrostatic loads, and will be based on
the following:
STRUCTURAL DESIGN CRITERIA
(
2-107-JJ
B-1-8
1. Flow Velocity or Gate Closure. See the Hydraulic
Design Criteria.
2. Hydrodynamic loads due to earthquake accelerations
will be based on formulation presented in the
Bureau of Reclamation Publication Design of
Gravity Dams, 1976 Edition, Page 70, repeated
below:
Where: Pe = Pressure normal to the face;
C = A dimensionless pressure coefficient;
o<.. = Horizontal earthauake acceleration;
Acceleration of gravity
w =
e =
Unit weight of water;
Depth of reservoir at section being
studied;
h = Vertical distance from the reservoir
surface to the elevation in question; and
~ = The maximum value of C for a given slope,
as obtained from Figure 4-18 page 71 of the
Bureau Publication and as reproduced as
Figure 1.
Load Combinations
For the various portions of the diversion tunnel identified
below, the following minimum loading combinations will be
examined to produce optimum, conservative design loads {see
1.3.3.1 for numbered loads):
STRUCTURAL DESIGN CRITERIA
/
2-107-JJ
B-1-9
1. Inlet Portal Structure
Load Combinations
a. 1+2
b. 1+2+12
c. 1+2+10
d. 1+2+3
e. 1+2+4
f. 1+2+(3 or 4)+6
g. 1+2+(3 or 4)+7
h. 1+2+5
Explanation
Normal rock loads combined w/
dead load.
As in "a" with snow
buildup.
load
As in "a" with construction
loads imposed from above.
As in "a" with external
hydrostatic effects.
As in "a" with internal
hydrostatic effects.
Hydrostatic pressure at normal
maximum water (el. 1180 feet)
with horizontal earthquake
acceleration of 0.75g, with a
50% increase in allowable
stress for steel but not to
exceed 90% of yield; ultimate
design load not to exceed U =
0.67 (1.4D+1.7L+1.87E) for
concrete with no increase in
allowable stress.
Hydrostatic pressure at normal
maximum water (el. 1180 feet)
with vertical earthquake
acceleration of 0. 50 g,
allowing same stress increase
conditions as in item "f"
above.
As in "a" with surge due to
sudden gate operation.
STRUCTURAL DESIGN CRITERIA
(
2-107-JJ
B-1-10
2. Bulkhead Gate Guide Structure
Bearing forces induced by loads on bulkhead gates.
3. Bulkhead Gates
Bulkhead gates shall be designed for the following
conditions:
a. 1+3
b. 1+3+6+8
c. 1+3+7+8
d. 1+4+9
4. Gate Shaft
Bulkhead gates in position
with PMF hydrostatic load.
Bulkhead gates in position
with normal maximum hydro-
static load and a 0.35 g
horizontal earthquake con-
ition causing hydrodynamic
load, with a 1/3 increase in
allowable stresses.
As in "b" above with 2/3 of
horizontal earthquake applied
as a vertical earthquake
loading, same allowable stress
increases.
Bulkhead gates lifted from
slots during normal headwater
elevation 1180 ft.
Gate shaft will be a "dry" shaft. Use same load
combinations as identified for tunnel liner design with
appropriate adjustments for configuration and orienta-
tion, as provided by the Responsible Geotechnical
Engineer.
STRUCTURAL DESIGN CRITERIA
2-107-JJ
B-1-11
5
@) Control and Service Gate Frame Structure and Gates
Load Combinations
a. 1+2
b. 1+2+(3 or 4)
c. 1+2+4+6+8
d. 1+2+4+7
e. 1 +2+4+5+9
f. 1+2+3+9
6. Liner for Tunnel
Load Combinations
a. 1+2+3
b. 1+2+4
c. 1+2+4+5
Explanation
Dead load with normal rock
loads.
As in "a" with hydrostatic
pressure.
Normal rock and hydrostatic
loads, combined with horizon-
tal earthquake acceleration of
0.75 g, with a 50% increase in
allowable stress for steel but
not to exceed 90% of yield;
ultimate design load not to
exceed U = 0.67 (1.4D+1.7L+
1.87E) for concrete with no
increase in allowable stress.
As in "c" except with vertical
earthquake acceleration of
0.50 g, same allowable stress
conditions.
As in "a" with gate operation.
Normal dead weight and rock
loads, external hydrostatic
pressures, tunnel drained,
gate being raised.
Exolanation
Tunnel empty with normal rock
& piezometric loads.
Tunnel full.
Normal dead and rock loads
with gate operation.
STRUCTURAL DESIGN CRITERIA
(
2-107-JJ
d. 1+2+(3 or 4)+6
e. 1+2+(3 or 4)+7
7. Penstock for Tunnel
B-1-12
Normal dead and rock loads,
hydrostatic pressure at normal
maximum water, with horizontal
earthquake acceleration of
0.75 g, with a 50% increase in
allowable stress for steel but
not to exceed 90% yield;
ultimate design load not to
exceed U = 0.67 (1.4D+1.7L+
1.87E) for concrete with no
increase in allowable stress.
As in "d" except with vertical
earthquake acceleration of
0.50g, same allowable stress
conditions.
Phase II Work -Later
8. Outlet Portal Structure
Load Combinations
a. 1+2+3
b. 1+2+4+5
c. 1+2+3+6
d. 1+2+3+7
Explanation
Dead loads with normal rock
loads and external hydrostatic
effects.
Normal dead and rock loads
with gate operation.
As in "a" with horizontal
earthquake acceleration of
0. 75 g, same allowable stress
conditions as 6, combination
"d" above.
As in "c" except with vertical
earthquake acceleration of
0.50 g.
STRUCTURAL DESIGN CRITERIA
e. 1+2+3+11+12
9. Gate House
Load Combinations
a. 1+12
b. 1+9+14
c. 1+13
d. 1 + ( 0. 50) 12+ 13
e. 1+6+(0.50)x12
f. 1+7+(0.50)x12
B-1-13
As in "an with snow build-up
and icing (due to spray
freeze-up. from 26 inch fish
water line flow diffusion and
diversion discharge during dam
construction).
Explanation
Normal dead loads with snow.
Dead loads plus live loads,
including equipment operation
loads.
Normal dead loads with wind.
Normal dead loads with wind
and snow.
Normal dead loads, horizontal
earthquake acceleration of
0.75 g and 50% snow load, with
a 50% increase 'in allowable
stress for steel but not to
exceed 90% yield; ultimate
design load not to exceed U =
0.67 (1.4D+1.7L+1.87E) for
concrete with no increase in
allowable stress.
Normal dead loads, vertical
earthquake acceleration of
0.50 g, same allowable stress
conditions as "d" above.
Note: Effects of air pressure differential due to gate operation
shall also be considered.
2-107-JJ STRUCTURAL DESIGN CRITERIA
(
B-1-14
1.4 DESIGN GUIDELINES
2-107-JJ
The following guidelines will be used in the design of the
diversion tunnel and appurtenant structures.
0 EM 1110-2-2901
0 Tunnel Lining
Army Corps of Engineers, Engineer
Manual, Engineering and Design
Tunnels and Shafts in Rock, Sept.
1978
Guidelines for Tunnel Lining Design
ASCE, T. D. O'Rourke, 1984
Design shall follow the rules and limits assigned below:
1. Concrete
ACI 318-83.
2. Structural Steel
Allowable stresses per AISC Specification
(AISC-78) to be kept within elastic range, unless
otherwise allowed.
3. Factors of Safety
The normal factors of safety developed within Part
A of this design criteria shall apply. No stress
increase factors will be allowed for design under
PMF conditions.
STRUCTURAL DESIGN CRITERIA
/
l
2-107-JJ
B-1-15
Factors of safety for structures on, in or an-
chored to rock shall be developed as required and
with the guidance of the Responsible Geotechnical
and Structural Engineers.
5. Special Physical Considerations
a. Reinforced Concrete
Concrete cover for reinforcing steel shall be
as follows:
(1) Tunnel liner-rock contact = 3 inches
(2) Tunnel liner-inside face = 4 inches
(3) Portal structure-rock contact = 3 inches
(4) Portal structure-exposed faces= 4 inches
b. Structural Steel
( 1) Bulkhead gates, control and service
gates -no corrosion allowance
(2) Gate guide -no corrosion allowance
STRUCTURAL DESIGN CRITERIA
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Extract p 71 Design of Gravity Dams -U.S. Bureau of Reclamation
Figure 1
HYDRAULIC DESIGN
CRITERIA -MAIN DAM
DIVERSION
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J. o. 15500
MAIN DAM DIVERSION
BIDRAQLIC DESIGN CBIIERIA
REVISION: 0
January 16, 1986
a:1-078-md HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
TABLE OF CONIEHTS
SECTION SECTION TITLE PAGE NO.
1.0 Description 1
2.0 Operation 3
3.0 Design Considerations 5
4.0 Design Criteria and Parameters 7
5.0 Selection of Equipment 8
a:1-078-md HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
Page 1
1 .0 DESCRIPTION
This document presents hydraulic design criteria for the intake,
tunnel, control and guard gates, fish flow release facilities,
and Bradley River channel, of the main dam diversion.
The diversion tunnel will be constructed to pass Bradley Lake
flows downstream during construction of the main dam and other
associated structures. The tunnel will also provide a means of
lowering the level of the completed reservoir at a controlled
rate as required during the project life in an emergency
condition. The tunnel facilities will allow downstream minimum
flow releases for the maintenance of aquatic habitat in the Lower
Bradley River.
The diversion tunnel will be constructed and operated in two
phases.
fhase I -Diversion Durin& Hain Dam Construction
A horseshoe shaped diversion tunnel will pass flows up to the
routed flood of record as a free surface flow. The tunnel will
be left unlined during Phase I.
The concrete intake structure will be completed during Phase I.
It will include one set of gate slots and upper portion of the
fish release piping. The flow section at the portal inlet is
rectangular with an arched ceiling. Transition to horseshoe
shape is provided. Bulkhead gates {2} will be made available
during Phase I. If' an emergency situation in the tunnel will
require its closure, the bulkhead gates will be lowered into the
slots. They can be used only f'or low flows. Water will be
discharged into the pool located at the exit of the tunnel. That
side of the pool opposite the tunnel will be rip-rapped to resist
a: 1-078-md HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
Page 2
erosion caused by the tunnel discharge during the construction.
Water from the pool will discharge into Bradley River channel.
fbase II -Bmercency Lake Drawdgwu
A vertical gate shaft will be bored near the middle of the
~el. The shaft will contain two high pressure gates installed
in a series. One gate will function as a guard gate and the
second as a control gate. Upper portion of the tunnel will be
lined with approximately 18-inch thick concrete liner. A steel
penstock will be installed downstream of the control gate and
will extend to the tunnel exit.
Minimum downstream flow releases to maintain aquatic habitat in
the Lower Bradley River will be through two steel pipes embedded
in the concrete floor of the tunnel • The two pipe intakes will
be located upstream of the tunnel inlet. Minimum flow releases
will be controlled with energy dissipation type valves or a
system of nozzles at the downstream end of the pipes outside the
tunnel outlet. The capability must be provided to adjust flow
releases at fine increments. To attain this incremental flow, it
may be necessary to manifold each pipe near the outlet to provide
multiple control valves per pipe. Structures will be built, one
on each side of the tunnel exit, to accommodate the control
valves and manifolds.
a: 1-078-md HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
Page 3
2.0 OPERATION
Phase I
The intake structure, unlined tunnel, and downstream channel
shall pass up to 4, 000 cfs in free flow condi tiona during the
main dam construction. This is based on uncontrolled release of
Lake inflows due to natural hydrologic events with the Lake level
initially at about El. 1068.
The bulkhead gates will be designed to close against the
diversion flow of approximately 500 of's. The corresponding flow
depth at the gate section is five feet. To minimize the total
vertical force on the gates during their lowering and raising,
several design features were adopted. Teflon coated seals and
stainless steel sealing surface will be provided. Also, teflon
coated bearing blocks will be provided. Seals against the sill
will be so arranged as to minimize the downpull force while
handling the gates under the flow.
It is recognized that after lowering the gates during the
construction period, the Lake level starts rising thus making
increasingly more difficult to raise the gates. Although teflon
is used on seals and bearing blocks, it appears that the depth of
water upstream of the gates, while closed, should not exceed 10
feet. Depths above 10 feet would produce vertical friction
forces of such a magnitude that the raising of gate may become
unfeasible and unsafe.
a:1-078-md HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
Page 4
Phase II
The water level of' the completed reservoir may require lowering
on a periodic basis to expose the dam face and associated
structures for purposes of' safety inspection and possible repair.
It is anticipated that this activity will be scheduled for the
periods ot low reservoir level , i.e. , March to May and further
lowering the reservoir level will be achieved by operating the
turbine--generator units at tull load on a continuous basis.
Operation of' the diversion tunnel for this purpose should be
avoided. Neither partial nor tull flow operations are desirable.
Partial gate opening causes undesirable slug flow and hydraulic
jUJilp in the discharge penstock, downstream of' the control gate.
Full flow discharged into the pool and into Bradley River channel
causes excessive erosion.
In the case of' a catastrophic earthquake, the Lake has to be
drawn down at a fast rate. The design discharge for this mode of'
operation is that required to draw down the reservoir in
approximately 45 days, yet limit the rate of' draw down to not
more than 2. 5 feet/ day to prevent damage to the lining of' the
main dam. During an emergency draw down, an average lake inflow
of' 1500 of's (two highest tlow months, July and August) and a no
flow condition through the powerhouse are assumed. The diversion
tunnel gates would be fully open during this entire draw down
period.
Fish release facilities will be operated so as to pass the
required flow through the two pipes up to the total of' 100 cf's.
At the lake levels close to the minimum level, both pipes will be
required to pass 100 cf's. For higher levels, one pipe only will
be able to pass the flow and the second may be shut down.
a: 1-078-md HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
Page 5
3.0 DESIGN CONSIDERATIONS
Phase I
The layout and elevation of the tunnel result in the need to
excavate the river channel at the tunnel outlet to El. 1060.
This arrangement offers the advantage of reducing the size of the
downstream cofferdam for main dam construction. The elevation of
the top of the upstream cofferdam and other structures acting· in
a similar fashion will need to be set at such an elevation as to
provide four feet of freeboard above El. 1086, which is based on
the steady state Lake level while passing 4,000 cts through the
tunnel.
During construction of the tunnel, a rock plug will be
temporarily lett in place to act as a cofferdam while the Lake
flow is passing through the natural Bradley River channel outlet.
During Phase I, the tunnel will be excavated and grouted. Tunnel
grouting must occur in Phase I prior to impounding the reservoir.
The initial drawdown of the Lake level from 1080 to 1068 may be
undertaken during the natural high flow period in the river.
This lower Lake level is obtained by removing the rock plug and
initiating diversion tunnel operations. Once the Lake is drawn
down, the construction of the cofferdam at the Bradley Lake
outlet and the main dam can proceed.
Improvements to the Bradley River channel downstream of the
diversion tunnel shall be made to provide sufficient cross-
sectional area and bottom slope to pass 4000 cts without causing
a backwater effect in the tunnel at that flow. Minimum freeboard
for the channel shall be four feet at 4000 cfs flow. The channel
shall be unlined excavated rock.
a:l-078-md HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
Page 6
Phase II
Upon completion of the main dam, the reservoir will be impounded
by installing the bulkhead gates at the diversion tunnel inlet.
Installation of the bulkhead gates should not be attempted when
diversion flows exceed 500 cfs. Immediately after the bulkhead
gates are installed, fish release piping will be completed and
the minimum required flow established. The installation of the
high pressure gates, the tunnel lining, penstock, and outlet
structure wUl follow. When the emergency discharge guard and
service gates are in place and operational, the bulkhead gates
wUl be removed using a barge. These gates and the penstock will
be sized to pass such flow as to lower the Lake from El. 1180 to
1090 in approximately 45 days with the gate fully open. The
gates and the penstock will have essentially the same flow area.
A curtain shall be provided on the downstream end of the Phase II
tunnel and penstock to retain natural heat during periods of low
temperatures.
The fish release control structures should be provided with
minimum heat to prevent freezing of flow equipment and allow
operations during winter.
Fish Fagilities
The fish bypass pipes must be designed to operate under reservoir
El. 1190.6. To limit stress caused by waterhammer within
allowable pipe stress, it is recommended to adjust closing time
of the control and guard valves to 10 seconds or more.
a: 1-078-md HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
Page 1
After the bulkhead gates are installed, the fish bypass piping
must be completed and the flow established as soon as possible.
Use of Victaulic type coupling is recommended to accelerate this
activity.
4.0 DESIGN CRITERIA AND PARAMETERS
In addition to the hydraulic criteria given below, refer to
Structural Criteria, Part B, Special Requirements and Design
Criteria for Major Structures, Section 1.0, Main Dam Diversion.
Phase I
Diversion Tunnel -
Cross section: modifed horseshoe, see attached sketches
Invert slope: tS (to facilitate construction)
Invert at concrete intake: El. 1068 (extending downstream of
bulkhead gate slot)
Manning's n: 0.015 (concrete)
0.040 (unlined rock)
Diversion Operation -
a: 1-078-md
Discharge: 4,000 cfs (routed flood of record)
Velocity: ~ 30 ft/sec (concrete at intake structure)
~ 20 ft/sec (unlined rock excavation)
~ 10 ft/sec (intake approach velocity)
Lake Level: El. 1086 (when passing 4000 cfs)
HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
Page 8
Phase II
Emergency draw down operation -
Initial reservoir level: El. 1180
Lowered reservoir level: El. 1072
Rate of draw down: 2 tt/day
Reservoir inflow:
El. 1180 to E. 1080: 1500 cts
Below El. 1080: 500 cts
Velocity in lined tunnel: ~ 30 tt/sec
Velocity in steel penstock: ~ 80 tt/sec
Total draw down time: 45 to 50 days
Minimum fish flow releases -
Discharge: 50 cts per pipe
Headwater: El. 1080
Tailwater: El. 1065
5. 0 SELECTION OF EQUIPMENT
Two steel bulkhead gates installed side by side will be used to
impound the reservoir. These gates will be removed when the
diversion tunnel system is complete and the high pressure gates
are in place. A means will be provided to till the upstream
portion of the tunnel to equalize the pressure on the bulkhead
gates when they are to be removed. The bulkhead gates will be
designed tor the hydrostatic load under the Lake El. 1190.6. The
bulkhead gates will have to close against 500 cts flow in the
open channel.
a:1-078-md HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
Page 9
The gate shaft will be or a dry well type construction. The
guard gate and the control gate will be hydraulic cylinder-
operated gates capable of throttling flow at varying gate
openings and should be of heavy duty construction to resist
potential vibrational loading. The maximum differential static
pressure on both the guard and control gates is that developed by
the Lake El. 1190.6. The gates will be so shaped that they
produce downpull at all conditions. Allowance will be made in
the gate design for pulsating hydrodynamic forces which are
expected to occur on the downstream side during the gate closing
and opening.
To provide head dissipation and incremental control of minimum
flow releases, hollow-cone valves or other means of energy
dissipation will be installed at the downstream end of the fish
bypass pipes along side the tunnel outlet.
A steel penstock of heavy duty welded construction will extend
from the control gate to the diversion tunnel exit and just
beyond the fish bypass housing structures. The penstock will be
anchored to a concrete bedding. Adequate support or the penstock
must be provided to resist the transient hydrodynamic force
occurring during gate operation.
a:1-078-md HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
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