Three-dimensional discrete element analysis of liquefaction behaviour of crushable pumice sand

Abstract

From an engineering viewpoint, pumice sand particles are problematic because of their crushability and compressibility. While laboratory and in-situ tests can be implemented to characterise their behaviour, these tests are generally time-consuming and expensive. In this paper, the liquefaction behaviour of crushable pumice sand specimens is examined using the Discrete Element Method (DEM). Each pumice particle is modelled as a sphere, which, when the maximum contact force reaches the limit condition, will break and split into 14-ball inscribed tangent spheres. Initially, the results of laboratory single-particle crushing tests are used to represent the breakage characteristics as a function of particle size. Next, using the open-source code YADE, 3D model specimens in a loose state are prepared and isotopically consolidated at prescribed levels of confining pressure. The numerical specimens are then subjected to cyclic loading under the undrained conditions. The results showed that the DEM model could replicate the laboratory-obtained experimental results, offering explanations on the effect of particle crushing on the cyclic deviator strain. The microscale observations also provide better insights into the evolution of force chains within the specimens, resulting in a clearer understanding of pumice sand behaviour during cyclic loading.