Comparing Liquefaction Evaluation Methods Using Penetration-V S Relationships Ronald D. Andrus Clemson University with P. Piratheepan, Brian S. Ellis, Jianfeng Zhang, and C. Hsein Juang U.S.-Taiwan Workshop on Soil Liquefaction National Chiao Tung University, Hsin-Chu, Taiwan November 3-5, 2003

Acknowledgements The U.S. Geological Survey (USGS) and the South Carolina Department of Transportation (SCDOT) funded part of this work Many individuals assisted with data collection, including: T. L. Holzer, M. J. Bennett, J. C. Tinsley, & T. E. Noce of USGS T. N. Adams of SCDOT T. J. Casey & W. B. Wright of Wright Padgett Christopher W. M. Camp & E. Cargill of S&ME, Inc. F. Syms of Bechtel Savannah River, Inc. S. L. Gassman of University of South Carolina

Database Data from California, South Carolina, Canada, Japan, and Taiwan 45 Holocene (< 10,000 years) soil layers, and 55 older soil layers Only sands with FC ≤ 20 % or I c ≤ 2.25 All measurements below water table Both non-liquefied and liquefied sites

Criteria for Selecting Data Thick, uniform soil layers based on CPT data, or several SPT and V S measurements Penetration test within 6 m of V s test At least 2 V s measurements and corresponding test intervals within layer Time history records used for V s determination have “easy picks” for shear wave arrivals; if time histories are not available, at least 3 V s measurements within layer

Corrected S-Wave Velocity where V S1 = stress-corrected V S (V S1 ) cs = stress- and fines content-corrected V S K cs = fines content correction factor (Juang et al. 2002) K a1 = age correction factor (Andrus & Stokoe 2000)

Three Curves for Evaluating Liquefaction Resistance

SPT – V S Relationships for Holocene Sands Age, years 500 Non-liquefied Liquefied

CPT - V S Relationships for Holocene Sands Age, years 500 Non-liquefied Liquefied

CPT – SPT Relationships for Holocene Sands Age, years 500 Non-liquefied Liquefied

V S – CRR Equation (Andrus & Stokoe 2000) where CRR 7.5cs = CRR curve for M W = 7.5 and FC ≤ 5 % (V S1 ) csa1 = corrected V S

New SPT – CRR Equation where CRR 7.5cs = CRR curve for M W = 7.5 and FC ≤ 5 % (N 1 ) 60cs = corrected SPT blow count

New CPT – CRR Equation where CRR 7.5cs = CRR curve for M W = 7.5 and I C ≤ 1.64 (q c1N ) cs = corrected CPT tip resistance

NEW CRR Curves Based on Penetration – V S Equations

Comparison of CRR Curves with Liquefaction Probability = 26 %

SPT - V S Relationships for Older Sands Ten Mile Hill (Liquefied)

CPT - V S Relationships for Older Sands Non-Liq Liq Merritt Sand Wando Ten Mile Hill Dry Branch Taiwan Sand

CPT – SPT Relationships for Older Sands Ten Mile Hill (Liquefied)

Age Scaling Factors for Penetration – V S Equations SPT-V S data CPT-V S data Age, years

Age Correction Factors Time (years) Age Correction Factor, K a1 (≈ 1/ASF) , , ,

Conclusions For the compiled Holocene data, the V S -based CRR curve by Andrus and Stokoe is on average more conservative than the SPT- and CPT-based curves. Values of V S from liquefied sands are lower than those from non-liquefied sands with similar penetration resistances. The penetration-V S equations developed for Holocene sands change by a factor of about per log cycle of time, based on data from non-liquefied sands. The V S -based CRR curve is characterized for soils with age of roughly 10 years; and new age scaling factors are proposed.