Microscopic investigation into liquefaction resistance of pre-sheared sand: Effects of particle shape and initial anisotropy

Liquefaction resistance of sand can be either increased or reduced due to an undrained cyclic pre-shearing depending on the degree of pre-shearing, which hinders a better prediction of liquefaction potential to be established. The mechanism of such changes in liquefaction resistance has been poorly understood. This contribution aims to gain micromechanical insights into pre-shearing effects on liquefaction resistance of sand using discrete element method (DEM) simulations. In particular, effects of particle shape and initial anisotropy on liquefaction resistance are investigated. The simulation results from samples consisting of non-spherical particles with an initial anisotropy can qualitatively capture the mechanical responses observed in equivalent laboratory experiments. The samples which yielded a qualitative agreement with the laboratory results are further analyzed micromechanically, and the relationships between liquefaction resistance and some microscopic parameters before cyclic loading are discussed. Microscopic analyses reveal that mean mechanical coordination number is well correlated with liquefaction resistance, whereas liquefaction resistance is less sensitive to anisotropy in particle orientation induced by pre-shearing. (C) 2021 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.