using Strength Ratios

Transcription

1 Shear Strength of Liquefied Soil using Strength Ratios Prof. Scott M. Olson, PhD, PE 86 th Annual Meeting Transportation Research Board January 22, 2007

2 Liquefaction Problems Photos from eeri.org

3 Undrained Behavior of Sand data from Verdugo (1992)

4 Behavior of Saturated, Contractive Sand under Sloping Ground s u (liq)/σ' vo

5 Liquefied Strength Ratio Concepts Olson & Stark (2003) data from Castro (1969)

6 Liquefied Strength Ratio Concepts Olson & Stark (2003)

7 Liquefied Strength Ratio Concepts Olson & Stark (2003)

8 Liquefied Strength Ratio Concepts Olson (2006)

9 s u u( (liq) from Flow Failures 60 Liquefi ied shear strength h, s u (kpa a) Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT after Olson & Stark (2002) Vertical Effective Stress, σ' vo (kpa)

10 Liquefied Strength Ratio v. q c1 0.4 Lique efied stre ength rati o, s u /σ' vo Back-calculated calculated liquefied strength ratio and measured CPT Back-calculated liquefied strength ratio and converted CPT from measured SPT Back-calculated liquefied strength ratio and estimated CPT Estimated liquefied strength ratio and measured, converted, or estimated CPT after Olson & Stark (2002) Normalized CPT tip resistance, q c1 (MPa)

11 Liquefied Shear Strength v. q c1 60 Liquefi ied shear strength h, s u (kpa a) Back-calculated calculated liquefied strength ratio and measured CPT Back-calculated liquefied strength ratio and converted CPT from measured SPT Back-calculated liquefied strength ratio and estimated CPT Estimated liquefied strength ratio and measured, converted, or estimated CPT Normalized CPT tip resistance, q c1 (MPa)

12 Liquefied Strength Ratio v. (N 1 1) Lique efied stre ength rati o, s u /σ' vo Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT after Olson & Stark (2002) Normalized SPT blow count, (N 1 ) 60

13 Liquefied Shear Strength v (N 1 1) Liquefi ied shear strength h, s u (kpa a) Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT Seed and Harder (1990) boundaries Normalized SPT blow count, (N 1 ) 60

14 Liquefied Shear Strength v. (N 1 1) 60cs 60 Liquefi ied shear strength h, s u (kpa a) Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT Seed and Harder (1990) boundaries Normalized SPT blow count, (N 1 ) 60cs

15 s u u( (liq) v. Vertical Effective Stress 60 Liquefi ied shear strength h, s u (kpa a) Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT after Olson & Stark (2002) Vertical Effective Stress, σ' vo (kpa)

16 Laboratory TxC Data Olson & Mattson (in press)

17 Laboratory DSS/RS Data Olson & Mattson (in press)

18 Laboratory TxE Data Olson & Mattson (in press)

19 Comparing Field and Lab Data Olson & Mattson (in press)

20 Behavior during Lateral Spreads Arumoli et al. (1992)

21 Idealized Behavior Shear Stress after Taboada & Dobry (1995) Shear Strain

22 s u (liq) from Lateral Spreads 60 Liquefi ied shear strength h, s u (kpa a) Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT Normalized SPT blow count, (N 1 ) 60

23 s u (liq) from Lateral Spreads Youd (1998)

24 s u (liq) from Lateral Spreads 60 Liquefi ied shear strength h, s u (kpa a) Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT Normalized SPT blow count, (N 1 ) 60cs

25 s u (liq)/σ' vo from Lateral Spreads 0.4 Lique efied stre ength rati o, s u /σ' vo Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT Normalized SPT blow count, (N 1 ) 60

26 Lateral Spreads in Luzon, Philippines 0.4 Lique efied stre ength rati o, s u /σ' vo Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT Normalized SPT blow count, (N 1 ) 60

27 Magnitude of Displacement 0.4 Lique efied stre ength rati o, s u /σ' vo Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT 2-5 m displacement m displacement Normalized SPT blow count, (N 1 ) 60

28 Strength of Shaking Lique efied stre ength rati o, s u /σ' vo Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT 0.17g 0.43g 0.51g 0.84g Normalized SPT blow count, (N 1 ) 60

29 Consolidation Stress Lique efied stre ength rati o, s u /σ' vo Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT Shake table test σ' vo ~44kPa 4.4 Miller Farm (Loma Prieta eq) σ' vo ~ 120 kpa Magsaysay Bridge (Luzon eq) σ' vo ~ 180 kpa Shake table test σ' vo ~ 3.4 kpa Normalized SPT blow count, (N 1 ) 60

30 Consolidation Stress 60 Liquefi ied shear strength h, s u (kpa a) Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT Vertical Effective Stress, σ' vo (kpa)

31 Void Ratio Redistribution Lique efied stre ength rati o, s u /σ' vo Back-calculated calculated liquefied strength ratio and measured SPT Back-calculated liquefied strength ratio and converted SPT from measured CPT Back-calculated liquefied strength ratio and estimated SPT Estimated liquefied strength ratio and measured, converted, or estimated SPT Shake table test Centrifuge experiment series Shake table test Normalized SPT blow count, (N 1 ) 60

32 Conclusions For many natural sands, s u (liq) consolidation stress s u (liq)/ σ ' vo 1 ψ s (liq)/ σ ' u vo penetration resistance

33 Conclusions TxC, DSS/RS, TxE support the liquefied strength ratio concept and suggest that mode of shear does not greatly affect s u /s' vo when specimens are contractive throughout shearing

34 Conclusions Lateral spreads appear to follow strength th ratio concept Suggests that we may not understand physics/mechanics very well Void ratio redistribution can only in part explain this as some field cases and many shake table/centrifuge tests consist of sand only no permeability contrast

35 Recommendations Practitioners can use relations between s u /σ' vo & q c1 [or (N 1 ) 60 ]t to evaluate post-triggering stability and deformation problems supported by theory supported by laboratory data supported field cases of liquefaction flow failures and lateral spreads

36 Thank You! Questions???

37 GO BEARS!!! superbowl.com chicagobears.com si.com

38 Simplified Liquefaction Analysis of Sloping Ground Susceptibility Is the soil contractive (i.e., Triggering Are loose the enough additional to Post-triggering triggering loads flow)? sufficient to ti trigger If liquefaction strain- does softening occur, what (i.e., are the liquefaction)? consequences (i.e., slope instability)? CONTRACTIVE DILATIVE

39 Liquefied Strength Ratio Concepts

40 Liquefied Strength Ratio Concepts

41 Analysis of Duncan Dam Olson (2006)