Georgia Tech

Session 1.2Soil Property Characterization

by In-Situ Tests

ISSMGEAugust 28, 2001

Georgia Tech

Session 1.2 - Soil Property Characterization by In-Situ Tests

Chair: Max Ervin (Australia)

Discussion Leader- Paul W. Mayne (USA)

Panel Members:

Martin Fahey (Western Australia)

Ranier Massarsch (Sweden)

An-Bin Huang (Taiwan)

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Session 1.2 - Soil Property Characterization by In-Situ Tests

Use of Enhanced In-Situ Tests, notably hybrid devices.

Importance of small-strain measurements in geotechnical deformation analyses

Reliability and Variability Issues

o Repeability of soundings

o Class ratings for equipment.

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Session 1.2 - In-Situ Tests

Question from Topic 1

Is it time to retire the Standard Penetration Test (SPT) ?

To consider this prospect

Let us go back - back in time

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Session 1.2 - In-Situ Tests

Question 1

Telephone 1909

Cell phone

2001

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Session 1.2 - In-Situ Tests

Question 1

Wright Plane 1903

Boeing 717

2001

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Session 1.2 - In-Situ Tests

Question 1

Oldfield Auto 1903

BMW

2001

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Session 1.2 - In-Situ Tests

Question 1

Geotech Test 1902

Geotech Test

2002 ?1902 - Colonial Charles Gowof Raymond Pile Company

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N

DR = relative

density

T = unit weight

LI = liquefaction index

' = friction angle

c' = cohesion intercept

eo = void ratio

qa = bearing

capacity

p' =

preconsolidation

Vs = shear wave

E' = Young's modulus

= dilatancy angle

qb = pile end

bearing

fs = pile skin

friction

SAND

cu = undrained

strength

T = unit weight

IR = rigidity index

' = friction angle

OCR = overconsolidation

K0 = lateral stress

state

eo = void ratio

Vs = shear wave

E' = Young's modulus

Cc = compression

index

qb = pile end bearing

fs = pile skin friction

k = permeability

qa = bearing stress

CLAY

Is One Number Enough???

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Use of In-Situ Tests

Numerical Simulations

Finite Elements Strain Path Finite Differences Discrete Elements

PLAXIS, FLAK, SEEP3d,ABAQUS, CRISP, ADINA,GEOSLOPE

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Enhanced In-Situ Tests

Cone Pressuremeter

Seismic Piezocone

Dilatocone

Seismic Dilatometer

Resisitivity Cone

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SCPTu Sounding, Memphis, Tennessee

Real-Time readings in computer screen

Penetration at 2 cm/s

Sand

Clay

Crust

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Shear Wave Velocity, Vs

Fundamental Measurement in all Solids (steel, concrete, wood, soils, rocks)

Initial small-strain stiffness represented by shear modulus: G0 = Vs

2 (alias Gdyn = Gmax = G0)

Applies to all static & dynamic problems at small strains (s < 10-6)

Applied to undrained & drained cases Need Reduction Factor for Relevant

Strain Levels.

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Modulus Degradation Schemes

Kondner (1963) Ramberg-Osgood Duncan & Chang

(1970) Seed & Idriss

(1971) Hardin & Drnevich

(1972) Jardine, et al.

(1986) Prevost & Keane

(1990)

Vucetic & Dobry (1991)

Tatsuoka & Shibuya (1992)

Fahey & Carter (1993) Whittle & Kavvadas

(1994) Puzrin & Burland

(1996, 1998) Tatsuoka, et al. (2001)

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PreFailure Deformation Characteristics of Geomaterials

Sapporo (1995): Edited by

Shibuya, Mitachi, & Miura.

London (1997): Edited by

Jardine, Davies, Hight, Smith, & Stallebrass.

Torino (1999): Edited by

Jamiolkowski, Lancellotta, & LoPresti.

Lyon (Sept. 22-24, 2003)

SPECIALTY CONFERENCES

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Enhanced In-Situ TestsSCPTu with Dissipation at Amherst Test

Site

0

2

4

6

8

10

12

14

16

0 1 2 3 4

Tip Stress, qt (MPa)

Dep

th (

m)

0

2

4

6

8

10

12

14

16

0 20 40 60 80

Sleeve fs (kPa)

0

2

4

6

8

10

12

14

16

-0.2 0 0.2 0.4 0.6

Porewater ub (MPa)

0

2

4

6

8

10

12

14

16

0 100 200 300 400

Shear Wave,VS (m/s)

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Enhanced In-Situ TestsSCPTu Prediction for DSS at Amherst Site

DSS Data from 8.6 m

0.0

0.1

0.2

0.3

0.4

0 1 2 3 4 5 6

Shear Strain, s (%)

No

rm.S

hear

Str

ess,

vo'

G91

G92

Modified Hyperbola

from SCPTu Data:

qT = 565 kPa

u2 = 414 kPa

Vs = 141 m/s

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SCPTu at Opelika Test Site, Alabama

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Axial Load Test at Opelika, Alabama

DrilledShaft 01(cased)

d = 0.91 mL = 11.0 m

Q (total)

Q shaft

Q base

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Topic 3: Reliability, Repeatability, Calibration, &

Interpretation Issues Prior Comparative Studies:

o Lunne, et al. (In-Situ'86)o Tanaka (CPT'95)

Electric vs. Electronic Penetrometers Subtraction vs. Tension Cones for fs

Smooth vs. Rough Steel - Interface affecting fs measurements.

Lunne, Robertson, & Powell (1997): Recommend different Class I to Class IV penetrometers for CPT work.

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Effective Strength Parameters

Bearing Capacity Theories Durgunoglu & Mitchell (1975); Vesic

(1977); Robertson & Campanella (1983); Salgado et al. (1994); Jamiolkowski & LoPresti (2000)

CSSM Dilatancy Approach using DR from CPT (Bolton, 1986)

Effective Stress Method (Senneset, Janbu & Sandven, 1989)

-’ (psi-phi)

“Sci-Fi”

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Session 1.2 - Summary

Geotechnical Investigations need to Employ Modern Technologies: Seismic Piezocone, Flat Dilatometer, Cone Pressuremeter, Geophysical Methods

Small-Strain Stiffness (G0) is Relevant

to Monotonic (Static) and Dynamic Geotechnical Problems

Address issues of Calibration,Equipment, Reliability, and Interpretation.

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Enhanced In-Situ Testing

Need more consistent methods for interpretation of in-situ tests:

Vane - Limit Equilbrium

Pressuremeter - Cavity Expansion

Piezocone - Strain Path

Pile Foundations - Limit Plasticity

Recommendations for Geotechnical Research

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Enhanced In-Situ Testing

Need additional numerical & analytical simulations of multiple tests using

Finite Elements

Strain Path Method

Discrete Elements

Finite Differences

Recommendations for Geotechnical Research

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Enhanced In-Situ Testing

Develop additional sensors + channels

New digital cone systems

Seismic Piezocone Pressuremeter

Dielectric-Resistitivity Seismic Piezocone

Gamma-EM-Dilatocone

Better use of statistical methods

Recommendations for Geotechnical Research

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