Presentation on theme: "Georgia Tech Session 1.2 Soil Property Characterization by In-Situ Tests ISSMGE August 28, 2001."— Presentation transcript:
Georgia Tech Session 1.2 Soil Property Characterization by In-Situ Tests ISSMGE August 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)
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.
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
Georgia Tech Session 1.2 - In-Situ Tests Question 1 Oldfield Auto 1903 BMW 2001
Georgia Tech Session 1.2 - In-Situ Tests Question 1 Geotech Test 1902 Geotech Test 2002 ? 1902 - Colonial Charles Gow of Raymond Pile Company
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???
Georgia Tech Use of In-Situ Tests Numerical Simulations Finite Elements Strain Path Finite Differences Discrete Elements PLAXIS, FLAK, SEEP3d, ABAQUS, CRISP, ADINA, GEOSLOPE
Georgia Tech SCPTu Sounding, Memphis, Tennessee Real-Time readings in computer screen Penetration at 2 cm/s Sand Clay Crust
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.
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
Georgia Tech Enhanced In-Situ Tests SCPTu with Dissipation at Amherst Test Site
Georgia Tech Enhanced In-Situ Tests SCPTu Prediction for DSS at Amherst Site
Georgia Tech SCPTu at Opelika Test Site, Alabama
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
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.
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
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.
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
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
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