Johns Hopkins University NSF Workshop Nov 2005 Integrated Site Characterization: In-Situ & Lab Testing with Constitutive Modeling Framework

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1 Johns Hopkins University NSF Workshop Nov 2005 Integrated Site Characterization: In-Situ & Lab Testing with Constitutive Modeling Framework Paul W. Mayne Professor, Geosystems Engineering Georgia Institute of Technology

2 NEWS FLASH (Feb 2004): NASA Unmanned Rovers "Spirit" and "Opportunity" find Red Dirt and Stones on Mars (Cost: US$820 Million) Haleakala Maui

3 Critical-State Soil Mechanics (CSSM) Underappreciated in geotech practice. Not generally taught in USA (and many other countries) at either undergrad and/or grad level. In USA, only current textbook which covers CSSM is Budhu (2000).

4 Shear Strength of Soils Without CSSM No actual "total strength" parameters: c-φ Use of term "cohesion" implies (?): Effective cohesion intercept (c') Undrained shear strength (c = c u = s u ) Yet neither of these is a fundamental property Too much emphasis on direct measurement of undrained shear strength in practice Too little emphasis on measurement of the effective friction angle: φ' = arcsin[3m c /(6+M c )]

5 Undrained Shear Strength Classical interpretation of CPT and VST in clays s u = q t σ N kt vo s u = 7 6T π d 3 Which s u? N kcpt = 15 and µ vane HC CIUC PSC CK 0 UC DSC DSS DS PSE CK 0 UC CIUE UU UC

6 Undrained Strength Modes Granta Gravel Bounding Surface Original Cam-Clay Cap Models Modified Cam Clay Nested Yield Surfaces Rotated Bullet MIT E-3 & S-1 Models Wroth-Prevost Constitutive Model NC Undrained Shear Strength Ratio Effective Stress Friction Angle (deg) CIUC KoPSC CKoUC SS DSS KoPSE CKoUE

7 CSSM for Shear Strength of Soils Effective stress framework in terms of Critical State Soil Mechanics (CSSM): Hvorslev (1937, 1960); Schofield & Wroth (1968); Burland (1968); Wood (1990). In most basic form: 3 soil properties (φ', C c, C s ) plus initial state (e 0, σ vo ', OCR) Examples: Cam-Clay, Modified Cam Clay, NorSand, Bounding Surface, Cap, Adachi, Ohta, Oka, Prévost nested yield surfaces; MIT Models E3 & S1 "Undrained" is just one specific stress path Yet!!! CSSM is missing from most textbooks and undergrad & grad curricula in the USA.

8 CSSM for Dummies Void Ratio, e C S C C CSL NC Void Ratio, e OC CSL NC Log σ v ' σ p ' Effective stress σ v ' CSL φ' = friction angle C c = compression index C s = swelling index Shear stress τ tanφ' Λ = 1- C s /C c Effective stress σ v ' σ p '

9 NC Undrained Strength in DSS 0.4 s u /σ vo ' NC (DSS) = ½ sinφ' su/σvo' NC (DSS) Bothkennar Amherst Hackensack James Bay Porto Tolle Boston Blue Silty Holocene Wroth (1984) Mexico City AGS Plastic Onsoy Rissa Portsmouth San Francisco Cowden Bootlegger sinφ'

10 Undrained Shear Strength from CSSM DSS Undrained Strength, su/σvo' 10 1 Intact φ' = 40 o 30 o 20 o s u /σ vo ' = ½ sinφ' OCR Λ Note: Λ = 0.8 Fissured Drammen Portsmouth Portland Maine Boston Blue Silty Holocene Haga Upper Chek Lok Lower Chek Lok Bangkok Atchafalaya Conn Valley Paria Hackensack McManus Cowden Brent Cross Overconsolidation Ratio, OCR Fissured 20

11 Porewater Pressure Response from CSSM Normalized Porewater Pressure, u/σvo' u s /σ vo ' = 1-0.5cosφ'OCR Λ Fissured Intact Λ = Drammen Portsmouth Portland Maine Boston Blue Silty Holocene Haga Upper Chek Lok Lower Chek Lok Bangkok Atchafalaya Conn Valley Paria Hackensack McManus Cowden Brent Cross Fissured 20 Overconsolidation Ratio, OCR

12 Port of Anchorage, Alaska Deviatoric Stress = q* = (σ 1-σ 3)/σ p' Bootlegger Cove Clay M c = (q/p') f = 1.10 M c = 6sinφ'/(3-sinφ') φ' = 27.7 o Strength Ratio, su/σvo' 10 1 Critical State Soil Mechanics (Modified Cam Clay) φ' = 27.7 o Λ = 0.75 DSS Data CIUC Data MCC Pred CIUC MCC Pred DSS Effective Stress, p'* = (σ 1 '+σ 2 '+σ 3 ')/(3σ p ') Overconsolidation Ratio, OCR

13 Cavity Expansion Critical State Method for Evaluating OCR in Clays from Piezocone Tests OCR = 2 1 qt u 195. M + 1 σ vo ' b 1/ Λ where M = 6 sinφ /(3-sinφ ) and Λ =1 C s /C c Overconsolidation Ratio, OCR f s u b Depth (meters) Bothkennar, UK CPTU CRS IL Oed RF q c q T 18 20

14 Diversity of Geomaterials

15 Complex Assortments of Parameters for Quantification of Geomaterials

16 Geotechnical Site Characterization What is Our Image to the Public? Every Soil Parameter from SPT N-value?

17 Geotechnical Site Characterization Professional Image in 2006

18 Deformation Characteristics of Geomaterials Importance of Small-Strain Stiffness SPECIALTY CONFERENCES Sapporo (1995): Shibuya, Mitachi, & Miura. London (1997): Jardine, Davies, Hight, Smith, & Stallebrass. Torino (1999): Jamiolkowski, Lancellotta, & LoPresti. TC 29 - Tatsuoka et al. (2001) Lyon (2003) Benedetto et al. Atlanta (2007) Rixet al.

19 G/G max Reduction Curves from MIT-S1 (Pestana & Whittle, 1999) ws = 0.5 ws = ws = 2 Normalized G/G max MIT S-1 Model (Pestana & Whittle, 1999) e o = 0.9; C b = 450 ω = 1; µ 0 ' = 0.2 p'/σ atm = 1.0 No Plastic Strains ws = 5 ws = Shear Strain, γ s (%)

20 Seismic Piezocone (SCPTu) Sounding Wolf River, Memphis, Tennessee 0 q t (MPa) f s (kpa) u 2 (kpa) V s (m/sec) d = 35.7 mm V s Depth (m) f s u q t

21 SCPTù in Piedmont Silts Atlanta Airport Runway 5 Five Independent Readings of Soil Behavior: q t, f s, u b, t 50, and V s. q T (MPa) f s (kpa) u b (kpa) t 50 (seconds) V s (m/s) Depth (m)

22 SCPTù 01 in Varved Clay University of Massachusetts, Amherst Tip Stress, q t (MPa) Sleeve f s (kpa) Porewater u b (MPa) Time Rate, t 50 (s) Shear Wave,V S (m/s) Depth (m) Note: dissipation data from DeGroot & Lutenegger

23 Seismic Piezocone Test (SCPTù) porewater pressure Normalized Q = (q t - σvo)/σvo' Soil Behavioral Classification Dissipations k h and c h log time Robertson (1990) Method sand silt clay Friction Ratio, FR = f s /(q t -σ vo ) I R = G/s u u o f s u 2 u 1 Geophones q T φ = fctn (Q, B q ) Deviatoric stress, q V S G max = ρ T V s 2 V P Void ratio, e shear stress, τ Stress-strain-strength Y 2 Y Y3 1 drained φ τ max s u Mean effective stress, p undrained S = degree of saturation (e o, σ vo ) One-Dimensional Consolidation σ p and OCR log vertical stress σ v M c = 6sinφ /(3-sinφ ) (q/p ) KoNC = 3sinφ /(3-2sinφ ) Fctn(σ p ) strength ratio, s u /σ vo SHANSEP or CSSM G shear strain, γ s log OCR

24 Drilling & Sampling Geophysics Constitutive Model Fully Integrated Ground Behavior Laboratory Testing Soil Parameters Evaluation e o, γ T, σ vo, D R, σ p, OCR, G o, D, K o, ν, φ, Ψ, Λ, Γ, c, k, c v, K, M, G, E, C c, C r, C s, C α, s u, E u In-Situ Testing Micromechanics Analytical Methods Constitutive Model Numerical Simulation

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