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Georgia Tech Session 1.2 Soil Property Characterization by In-Situ Tests ISSMGE August 28, 2001.

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Presentation on theme: "Georgia Tech Session 1.2 Soil Property Characterization by In-Situ Tests ISSMGE August 28, 2001."— Presentation transcript:

1 Georgia Tech Session 1.2 Soil Property Characterization by In-Situ Tests ISSMGE August 28, 2001

2 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)

3 Georgia Tech 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 oRepeability of soundings oClass ratings for equipment.

4 Georgia Tech 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

5 Georgia Tech Session 1.2 - In-Situ Tests Question 1 Telephone 1909 Cell phone 2001

6 Georgia Tech Session 1.2 - In-Situ Tests Question 1 Wright Plane 1903 Boeing 717 2001

7 Georgia Tech Session 1.2 - In-Situ Tests Question 1 Oldfield Auto 1903 BMW 2001

8 Georgia Tech Session 1.2 - In-Situ Tests Question 1 Geotech Test 1902 Geotech Test 2002 ? 1902 - Colonial Charles Gow of Raymond Pile Company

9 Georgia Tech N D R = relative density T = unit weight LI = liquefaction index ' = friction angle c' = cohesion intercept e o = void ratio q a = bearing capacity p ' = preconsolidation V s = shear wave E' = Young's modulus = dilatancy angle q b = pile end bearing f s = pile skin friction SAND c u = undrained strength T = unit weight I R = rigidity index ' = friction angle OCR = overconsolidation K 0 = lateral stress state e o = void ratio V s = shear wave E' = Young's modulus C c = compression index q b = pile end bearing f s = pile skin friction k = permeability q a = bearing stress CLAY Is One Number Enough???

10 Georgia Tech Use of In-Situ Tests Numerical Simulations Finite Elements Strain Path Finite Differences Discrete Elements PLAXIS, FLAK, SEEP3d, ABAQUS, CRISP, ADINA, GEOSLOPE

11 Georgia Tech Enhanced In-Situ Tests Cone Pressuremeter Seismic Piezocone Dilatocone Seismic Dilatometer Resisitivity Cone

12 Georgia Tech SCPTu Sounding, Memphis, Tennessee Real-Time readings in computer screen Penetration at 2 cm/s Sand Clay Crust

13 Georgia Tech Shear Wave Velocity, V s Fundamental Measurement in all Solids (steel, concrete, wood, soils, rocks) Initial small-strain stiffness represented by shear modulus: G 0 = V s 2 (alias G dyn = G max = G 0 ) Applies to all static & dynamic problems at small strains ( s < 10 -6 ) Applied to undrained & drained cases Need Reduction Factor for Relevant Strain Levels.

14 Georgia Tech 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)

15 Georgia Tech 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

16 Georgia Tech Enhanced In-Situ Tests SCPTu with Dissipation at Amherst Test Site

17 Georgia Tech Enhanced In-Situ Tests SCPTu Prediction for DSS at Amherst Site

18 Georgia Tech SCPTu at Opelika Test Site, Alabama

19 Georgia Tech Axial Load Test at Opelika, Alabama Drilled Shaft 01 (cased) d = 0.91 m L = 11.0 m Q (total) Q shaft Q base

20 Georgia Tech Topic 3: Reliability, Repeatability, Calibration, & Interpretation Issues Prior Comparative Studies: oLunne, et al. (In-Situ'86) oTanaka (CPT'95) Electric vs. Electronic Penetrometers Subtraction vs. Tension Cones for f s Smooth vs. Rough Steel - Interface affecting f s measurements. Lunne, Robertson, & Powell (1997): Recommend different Class I to Class IV penetrometers for CPT work.

21 Georgia Tech 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 D R from CPT (Bolton, 1986) Effective Stress Method (Senneset, Janbu & Sandven, 1989) - (psi-phi) Sci-Fi

22 Georgia Tech Session 1.2 - Summary Geotechnical Investigations need to Employ Modern Technologies: Seismic Piezocone, Flat Dilatometer, Cone Pressuremeter, Geophysical Methods Small-Strain Stiffness (G 0 ) is Relevant to Monotonic (Static) and Dynamic Geotechnical Problems Address issues of Calibration,Equipment, Reliability, and Interpretation.

23 Georgia Tech

24 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

25 Georgia Tech 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

26 Georgia Tech 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

27 Georgia Tech


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