Pre- and Post-Liquefaction Response of Sand in Cyclic Simple Shear

This paper deals with pre- and post-liquefaction behaviour of a silica sand tested under simple shear (SS) loading conditions. Post-liquefaction response was investigated taking into account two main features: evaluation of liquefaction-induced volumetric strains resulting from the "dissipation" of pore water pressures; assessment of re-liquefaction characteristics of sand which has previously experienced liquefaction under the first loading. To this purpose, loose and dense reconstituted specimens were subjected to a first cyclic loading in undrained conditions. After reconsolidation, cyclic shear stresses with the same amplitude were again applied to the specimens (second loading or re-loading). With respect to the first liquefaction, a relationship between the normalized cyclic shear stresses and the normalized phase transformation strength obtained from monotonic tests was established regardless of relative density of material. The liquefaction-induced deformations obtained after re-consolidation were found to be well in agreement with those predicted by other approaches proposed in literature. Finally, it was also found that the change in liquefaction resistance of liquefied sand was affected by the relative density of the tested sand.