Soil%20Property%20Characterization%20by%20In-Situ%20Tests

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Session 1.2 Soil Property Characterization by
In-Situ Tests
ISSMGE August 28, 2001
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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
• Repeability of soundings
• Class ratings for equipment.

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Session 1.2 - In-Situ TestsQuestion 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 TestsQuestion 1

• Telephone 1909

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Session 1.2 - In-Situ TestsQuestion 1

• Wright Plane 1903

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Session 1.2 - In-Situ TestsQuestion 1

• Oldfield Auto 1903

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Session 1.2 - In-Situ TestsQuestion 1

• Geotech Test 1902

1902 - Colonial Charles Gow of Raymond Pile
Company
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Is One Number Enough???
N
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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
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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 r Vs2 (alias Gdyn
  Gmax G0)
• Applies to all static dynamic problems at small
  strains (gs lt 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
SPECIALTY CONFERENCES

• 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)

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Enhanced In-Situ TestsSCPTu with Dissipation at
Amherst Test Site
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Enhanced In-Situ TestsSCPTu Prediction for DSS
at Amherst Site
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SCPTu at Opelika Test Site, Alabama
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Axial Load Test at Opelika, Alabama
Q (total)
Drilled Shaft 01 (cased) d 0.91 m L 11.0 m
Q shaft
Q base
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Topic 3 Reliability, Repeatability, Calibration,
Interpretation Issues

• Prior Comparative Studies
• Lunne, et al. (In-Situ'86)
• 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)

y-f (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
Recommendations for Geotechnical Research

• Need more consistent methods for interpretation
  of in-situ tests
• Vane - Limit Equilbrium
• Pressuremeter - Cavity Expansion
• Piezocone - Strain Path
• Pile Foundations - Limit Plasticity

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Enhanced In-Situ Testing
Recommendations for Geotechnical Research

• Need additional numerical analytical
  simulations of multiple tests using
• Finite Elements
• Strain Path Method
• Discrete Elements
• Finite Differences

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Enhanced In-Situ Testing
Recommendations for Geotechnical Research

• Develop additional sensors channels
• New digital cone systems
• Seismic Piezocone Pressuremeter
• Dielectric-Resistitivity Seismic Piezocone
• Gamma-EM-Dilatocone
• Better use of statistical methods

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