Transcript Geotechnical and Seismic Design Aspects of the SR 75-282 Tunnel in Coronado, California Jim Gingery, PE, GE Principal Engineer, Kleinfelder, San Diego PhD Student, University.

Geotechnical and Seismic Design
Aspects of the SR 75-282 Tunnel in
Coronado, California
Jim Gingery, PE, GE
Principal Engineer, Kleinfelder, San Diego
PhD Student, University of California San Diego
Overview of Presentation
 Project Background
 General Geotechnical Evaluations
 Seismic Tunnel Design
Fault Hazard Evaluations
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Project Background
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Current and Future of Project Phases
 Project is in planning and preliminary engineering
phase with several different alternatives considered,
including two tunnels.
 Final design will be on selected alternative and will
involve additional geotechnical study
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PROJECT LOCATION
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Project Project Location
PROPOSED TUNNEL
ALIGNMENT
PROJECT LOCATION
PROJECT LOCATION
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Tunnel Alternatives Under Consideration
15 m X 6 m Box
Cut & Cover
11.5 m Diam.
Twin Bores
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General Geotechnical Evaluations
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Phase 1 Field Investigation
Previous work: 4 borings/wells and 5 CPTs by Golder, 1 Caltrans boring
Phase 1 Study by Kleinfelder:
7 Rotary Wash Borings
2 Resonant Sonic Borings
9 CPTs Soundings and 3 Seismic CPTs
800-foot High Definition Seismic Reflection Line (night work)
2 existing groundwater monitoring wells sampled
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Laboratory Analyses
Geotechnical
Laboratory Testing
Environmental
Groundwater Testing
Environmental
Soil Testing
Sieve
Atterberg Lim.
Moisture/Dens.
Consolidation
UU Triaxial
CU Triaxial
Direct Shear
Corrosivity
TPH
VOCs
SVOCs
PCBs
Metals
Corrosivity
Salinity
Hardness
Density
and more
TPH
VOCs
SVOCs
Metals
Corrosivity
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Regional Geology
(Kennedy & Tan (2005)
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Local
Geology
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Site Stratigraphy
Fill
Bay Deposits
Eolian Deposits
Fill
Bay Point Formation –
Sand and Silty Sand
Tunnel (schematic)
Bay Point Formation –
Interbedded Sand, Silt and Clay
Coronado
Fault
Note: 20X Vertical exaggeration
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Engineering Properties of Sand
Raw CPT and SPT Data
Relative Density vs. Elevation
NON-PLASTIC BAYPOINT FORMATION ONLY
Normalized and Corrected: qc1N, (N1)60
30
10
Converted to Dr:
DR 
qc1N
305 QC  QOCR
DR 
( N1 ) 60
C P  C A  COCR
(Kulhawy & Mayne, 1990)
Elevation (feet)
-10
-30
SPT Data Points
-50
CPT Data
Statistically analyzed and
subdivided by material and
elevation bins with COV < 0.45
 and f’ estimated
(NAVFAC DM 7.1, 1986)
-70
Step Function
Boundaries
Mean
-90
Mean +/- 1STDEV
-110
0
10 20 30 40 50 60 70 80 90 100
Relative Density, Dr (percent)
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Engineering Properties of Clay
20
20
Unit weights estimated
based on statistical
analysis of lab data.
0
0
Su from Laboratory CU tests
Natural Water
Content
Su from SHANSEP Calculations
-20
-20
-40
-60
Recommended Design Su Profile
for Clays and Clayey Silts
Elevation (feet)
Elevation (feet)
Undrained shear strength
estimated based on:
UU Triaxial
CU Triaxial
SHANSEP and
consol tests
Su from Laboratory UU tests
Plastic and Liquid
Limits
-40
-60
4100 psf
-80
-80
-100
-100
-120
-120
0 10 20 30 40 50 60 70 80
Plastic Lim it, Liquid Lim it, Water Content
(percent)
5150 psf
0
2,000 4,000 6,000 8,000 10,000 12,000
Undrained Shear Strength, Su (psf)
(in triaxial compression at lab strain rate)
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Seismic Tunnel Design
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San Diego
Regional
Fault Map
Wide zone of faulting
from San Andreas to
offshore of San Diego
Rose Canyon Fault Zone
most dominant structure
in San Diego region
Site Area
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Historic Seismicity Map
Source: Goter (1995)
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Crustal Velocity
Vectors in Southern
California
~ 40 mm/year (1.6 inches/year)
of differential movement is
occurring across the greater
San Andreas fault zone.
Site
Only 1 to 2 mm/year on the
Rose Canyon Fault Zone
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Faults in the
San Diego
Metro Area
Source: Treiman (1993)
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Results of Seismic Hazard Analysis
(Combination of PSHA and deterministic analyses)
PGA
Functional Evaluation
Earthquake
(72-year return period)
Safety Evaluation
Earthquake
(975-year+deterministic)
0.12g
0.70g
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Earthquake Effects on Tunnels
Displacement-based design
Types of displacements considered:
Longitudinal shear and/or surface wave passage
Vertically propagating shear waves
Permanent displacements due to fault offset
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Earthquake Effects on Tunnels
Longitudinal Bending
Seismic
Waves
Longitudinal
Due to Wave Passage
TunnelBending
Prior to Earthquake
During an Earthquake
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Earthquake Effects on Tunnels
Compression/Extension
Tension
Compression
Tension
Seismic
Waves
Tunnel
During
Earthquake
Tunnel
Prior
to Earthquake
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Seismic Tunnel Design, Tunnel-Soil Interaction
Psuedo-static beam on non-linear foundation
Springs estimated
using FLAC
Longitudinal Bending Due to Wave Passage
Including Tunnel-Soil Interaction Effects
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Seismic Tunnel Design, Tunnel-Soil Interaction
Springs estimated
using FLAC
Displacement versus Force
1,600,000
Sample Displacement
Contours from FLAC model
Force (pounds)
1,200,000
Case 13 Horz.
800,000
Case 14 Up
Case 15 Down
400,000
Longitudinal
0
0
1
2
3
Displacement (feet)
4
5
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Ovaling and Racking
Vertically Propagating
Shear Waves
1

Cyclic shear strain (cyc )
was estimated using
Tokimatsu and Seed
(1987).
The peak shear strain
was then taken as:
 = cyc/0.65
Ovaling
of
Circular
Circular Tunnel
Racking of
and Rectangular Tunnel
Rectangular Tunnel
Prior to Earthquake
MLE (Caltrans Deterministic)
Peak Shear Strain, 
(percent)
0.34
OLE with 150-year return period
0.04
OLE with 72-year return period
0.03
Design Earthquake Event
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Fault Hazard Evaluation
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Faults in the
San Diego
Metro Area
Source: Treiman (1993)
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Suspected
Fault
Scarp
and
AP-Zones
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Seismic Refraction Data & Interpretation
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Bucket Auger Holes and
Row of Closely-Spaced CPTs
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CPT Profile
Faulting observed
Faulting not observed
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CPT Profile – faulted zone
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Fault Trench Exploration Photos
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Logging the Trench
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Fault Trench Log
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Fault Trench Log
Max Holocene offset
i.e. A-E contact
11.5 inches vertical
(0.3 m) throw
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Four Models Considered for Strike-Slip
Offset Estimation:
Independent Rupture (Wells & Coppersmith,
1994)
Extensional Faulting Kinematic Model
Wrench Faulting Kinematic Model
“Horsetail” Model
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Independent Rupture Model using
Wells & Coppersmith (1994)
Median Average Displacement:
Log(AD) = -1.70 + 1.04 log(SRL)
For SRL=12 km, AD = 0.26 m = 10 inches
Median Maximum Displacement:
Log(MD) = -1.69 + 1.16 log(SRL)
For SRL=12 km; AD = 0.36 m = 14 inches
Map: Treiman
(1993)
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Kinematic Fault Models
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Extensional
Fault Model
Model Predicts 5 inches
of RL movement
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Wrench Fault
Kinematic Model
Model Predicts 5 to 10
inches of LL movement
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“Horsetail”
Fault Model
Model Predicts 22 inches
of RL movement
The 3 meters of strike
slip displacement on the
Rose Canyon (master)
fault is partitioned evenly
to the Spanish Bight,
Coronado, Silver Strand
and San Diego Bay
faults.
Note:
SB = Spanish Bight fault
C = Coronado fault
SS = Silver Strand fault
SDB = San Diego Bay faults
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Design Dip Slip Profile
0.6 m wide primary
zone
16 m wide
secondary zone
5 cm
(10%)
16 m wide
secondary zone
30 cm 15 cm
(60%) (30%)
Not to Scale
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Design Strike Slip Profile
0.6 m wide primary
zone
16 m wide
secondary zone
28 cm RL
18 cm LL
(25%)
16 m wide
secondary zone
56 cm RL
36 cm LL
(50%)
28 cm RL
18 cm LL
(25%)
Not to Scale
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Fault Offset Tunnel-Soil Interaction
Displacements
Free Field Soil
Springs estimated
using FLAC
Fault
Longitudinal Bending Due to Fault Offset
Including Tunnel-Soil Interaction Effects
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Tunnel-Soil Interaction –
3D FLAC Modeling by Tunnel Designer,
Hatch Mott MacDonald
After Gregor et al. (2006)
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Project Team
Project Team:
City of Coronado, Owner
Parsons Brinckerhoff, Prime
Hatch Mott MacDonald, Tunnel Design
Kleinfelder, Inc.
Caltrans-Appointed Technical Advisory Panel
Dr. Norm Abrahamson (PG&E)
Dr. Clarence Allen (Caltech)
Dr. Jonathan Bray (U.C. Berkeley)
Dr. Tor Brekke (U.C. Berkeley, Emeritus)
Mr. Ignutius Po Lam (Earth Mechanics)
Kleinfelder Subconsultant:
Dr. Kevin Coppersmith (Consultant)
Tom Rockwell, ECI/SDSU
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Thank You!
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