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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