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