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PURDUE GEOTECHNICAL SOCIETY WORKSHOP
GEOTECHNICS AND SUPPLYING FUTURE ENERGY NEEDS
Monday, May 7, 2007
GEOTECHNICAL GEOPHYSICS FOR POWER DEVELOPMENT
• RICHARD D. WOODSProfessor Emeritus, Univ. of MichiganMelchor Visiting Professor Notre Dame University
DESIGN BASED ON STRAIN
What we can do but usually don’t.
Let’s catch up to the Civil World.
Easy to measure moduli insitu.
1st to do it: Bill Swiger1974 - - Nuclear Power• Stone and Webster heavily into
nuclear power development.
• Used G/E from seismic waves to design for settlement.
• TAMU Settlement Conference, several settlement methods used In prediction challenge including seismic modulus.
TAMU SETTLEMENTCHALLENGE, 1994
Predicting Foundation Settlements
T-Rex: Loading with Shear (SV) Waves
Vertically Propagating Shear (SV) Waves
ShallowInstrumented Zone
Solutions - Static Conditions1. Static Loading
• foundation settlements• retaining wall movements
2. Site Characterization• layering, ground water table, etc.• underground cavity detection• tunnel investigations• pavement studies
3. Process Monitoring• grouting evaluations• ground improvement studies• areas of deterioration
Field Measurementswith Compression (P) and Shear (S) Waves
Gmax = VS2γt
g
Mmax = Vp2γt
g
Small-StrainModulus
Distortion
Vp
VS
Wave Velocity
ParticleMotion
WaveType
P
S
TOTAL WAVE FIELD
B WO AL VT E
S
WIND FARMS
CURRENT APPLICATION OF FOUNDATION DESIGN
EARLY WINDFARM
SPAIN
GREENPARK
UK
WIND POWER FACTS• WORLDWIDE: 74,000 MW, 2006• ALTAMONT PASS: USA FAMOUS
SITE, 6000 TURBINES @ 20 kW ea• NEW MODELS 100 kW ea minimum• COST $1600 per kW installed• COST COMPETETIVE: GAS $52.50,
COAL $53.10, and WIND $55.80/MWh
• POWER AVAILABLE % TIME: Nuclear 90%, Coal 70%, Wind 35%
WIND-ALTAMONTAltamont Pass, CA
6000 @ 20kW = 125 MW & Annual bird kill
ECONOMIES
• Groups of footings could be designed individually based on ground profile
• Each footing could be customized to minimize cost
EXAMPLE
MAGRATH WIND FARM, ALBERTAREVISED SPACING
00 0.05 0.10 0.15
Shear Strain, γ (%)
Shear Stress,τ (kPa)
Gmax
Small-strainwave propagation: Gmax = VS
2
Small-Strain SeismicMeasurements
γ τ
τInitial Loading Curve
γtg
1. Soil Profile 2. Field: Linear Vs (and Vp)
3. Lab: Linear and Nonlinear G and D
60
40
Dep
th, m20
0
450300Vs, m/s
1500
Sand(SP)
Clay(CH)
Silt(ML)
Sand(SW)
Clay(CL)
G,MPa
Gmax
120
0
DminD,%
16
00.001 0.1
Shear Strain, γ , %
0.001 0.1
Gmax = ρvs2
Role of Stress WaveMeasurements
2. P-S Suspension Logger
1. Surface Wave (SASW) Test
*
*
Recent Field Methods(1990s)
Direct P and S Waves
MeasureRayleigh
(R) Waves
Source Point 1 Point 2
*
Stress Wave (Seismic)Measurements in the Field
Objective: measure time, t, for a given stress wave to propagate a givendistance, d ... then velocity = d/t
d
Key characteristic: small-strain (linear) measurements
VARIABLE SCALE
Tunnel Investigation
ConcreteLiner
Grout
Rock
tconcrete
tgrout
Conducting SASW TestsSmall Hammer
Accelerometers
0
2
4
6
80 1000 3000
Shear Wave Velocity, VS , m/sec2000 4000
Station 1(Springline)
Depth,m
Concrete Liner
Rock
Interpreted VS Profile Behind Tunnel Wall at Springline
Results:1. high-quality
concrete2. thickness ~
0.3 m3. no voids4. rock stiffer
than liner
Some Questions
1 .Quality of concrete liner?2. Thickness of concrete liner?3. Quality of grout in crown?4. Thickness of grout in crown?5. Any voids behind liner?6. Stiffness of rock behind liner?
(Answered all Questions)
1.
VINCENTTHOMASBRIDGE,Liquefaction
CRAWLER VEHICLE AS SOURCE
VIBROSEIS
Site response, soil-structure interaction, liquefaction, etc.
Solutions -Dynamic Conditions
POWER PLANT SITING
-EATHQUAKE HAZARD-SEISMOMETER SITES ARE
USUALLY NOT WELL CHARACTERIZED
Predict Ground MotionsDuring Earthquake Shaking
BEDROCK
SOIL LAYER 1
SOIL LAYER 2
SOIL LAYER ..
SOIL LAYER n
-0.5
0.0
0.5
6050403020100
Time, sec
Time, sec
-0.5
0.0
0.5
6050403020100
uground..
ubedrock..
Ground Accel,
u, g..
Bedrock Accel,
u, g..
150
100
50
0
Depth,m
0.200.150.100.050.00Shearing Strain, γ , %
Peak Shearing Strains: La Cienega
Mean
Mean - σ
Mean + σ
from Dr. Walt Silva, Pacific Engineering and Analysis
POWER PLANT SITING
HIDDEN GROUND CAVITIESDavis Besey, OhioSan Onofre, Cal
DRIC E
D PE RT OR F0 II LT E
SALT
SOLUTION MINING
CANADIANSINKHOLES
Geophysics is Playing anIncreasing Role in Solving General
Geotechnical Engineering Problems
Case Histories and Applications
• static conditions
• dynamic conditions
Conclusions andFuture Developments
Stress wave (seismic) measurements play an important role in geotechnical engineering.
This role will continue to grow.
The growth will involve four areas: 1. education, 2. integration, 3. automation, and4. innovation.
USES OF GEOPHYSICS IN POWER DEVELOPMENT
• SMALL SCALE GEOTECHNICAL ACTIVITES – FOOTINGS FOR WIND FARMS
TO• LARGE SCALE GEOTECHNICAL
ACTIVITES – SITING FOR LARGE POWER PLANTS
MANY THANKS FROM ME TO:
• PURDUE GEOTECHNICAL SOCIETY FOR INCLUDING THIS “IRISH WOLVERINE”
• PROF. VINCENT DRNEVICH
• ALL IN ATTENDENCE
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