Effects of prior non-liquefying undrained cyclic loading on sand liquefaction resistance via discrete element analysis

Abstract

Earthquake cases demonstrate that prior earthquakes have critical impacts on the liquefaction resistance of sandy soils during subsequent earthquakes. Most previous studies focused on the influence of previous liquefaction events on soil reliquefaction resistance, while few have investigated the effects of prior non-liquefying undrained cyclic loading history on the liquefaction resistance. In this study, discrete element method (DEM) was employed to simulate the liquefaction behaviors of triaxial specimens reconsolidated from non-liquefying states during prior undrained cyclic tests with various cyclic stress ratios (CSRs). Results showed that prior non-liquefying loading could increase or decrease the sand liquefaction resistance, which significantly depended on the CSR of the prior loading and the excess pore pressure ratio (ru) caused during the prior loading. Specimens that were previously loaded under larger CSRs had stronger anisotropy and fewer interparticle contacts after reconsolidation and thereby exhibited lower liquefaction resistance, while specimens that were reconsolidated from prior tests with smaller CSRs had weaker anisotropy and more interparticle contacts and thus exhibited obviously higher liquefaction resistance. Sand liquefaction resistance after a prior non-liquefying loading was well correlated with initial anisotropic degree and mechanical average coordination number.