Cyclic resistance and liquefaction behavior of silt and sandy silt soils

Abstract

The liquefaction behavior and cyclic resistance ratio (CRR) of reconstituted samples of non-plastic silt and sandy silts with 50% and 75% silt content are examined using constant-volume cyclic and monotonic ring shear tests along with bender element shear wave velocity (V_s) measurements.  Liquefaction occurred at excess pore water pressure ratios (r_u) between 0.6 and 0.7 associated with cumulative cyclic shear strains (y) of 4% to 7%, after which cyclic liquefaction ensured with very large shear strains and excess pore water pressure ratio (r_u>0.8).  The cyclic ring shear tests demonstrate that cyclic resistance ratio of silt and sandy silts decreases with increasing void ratio, or with decreasing silt content at a certain void ratio.  The results also show good agreement with those from cyclic direct simple shear tests on silts and sandy silts.  A unique correlation is developed for estimating CRR of silts and sandy silts (with more than 50% silt content) from stress-normalized shear wave velocity measurements (V_s1) with negligible effect of silt content.  The results indicate that the existing CRR-V_s1 correlations would underestimate the liquefaction resistance of silts and sandy silt soils.