Effect of Stress Reversal and Consolidation on Undrained Behaviour of Granular Materials under Cyclic Loading: A DEM Study

The undrained behaviour of granular materials under cyclic loading is highly influenced by various parameters such as void ratio (e), confining stress (p'), initial static shear stress (q(s)), cyclic deviatoric stress (q(cyc)), stress reversal (SR), and no-stress reversal (NSR) conditions. Extensive studies have been conducted for evaluating the influence of e, p', q(cyc), and SR on isotropically consolidated specimens. However, a soil element in nature is usually in anisotropically or K-0 consolidated state and hence subjected to a q(s). Literature suggests that the variation of q(s) may affect the pore water pressure (Delta u) generation, strain (epsilon(d)) accumulation, and fabric (F) even for same e and p'. Current study is a preliminary investigation in evaluating the combined effect of q(s) and q(cyc) on cyclic liquefaction behaviour of K-0-consolidated soils. Cyclic triaxial simulations were conducted using discrete element method (DEM) on an assemblage of spherical particles. It was found that SR and NSR played a significant role in defining the failure mechanism which is dependent on the magnitude of q(s) and q(cyc). In addition to macro study, this study also revealed that micro parameters CN and F-vM can be used for defining the point of initial liquefaction.