Numerical simulations of two-dimensional saturated granular media

Abstract

The liquefaction phenomenon in soil has been studied in great detail during the past 20 years. The need to understand this phenomenon has been emphasized by the extent of the damages resulting from soil liquefaction during earthquakes. Although an overall explanation exists for this phenomenon through the concept of effective. stress, the basic mechanism of loss of strength of the soil skeleton has not been thoroughly examined and remains unclear. The present study proposes a numerical model for simulations of the behavior of saturated granular media. The model was developed with two main objectives: 1. To represent the mechanical response of an assemblage of discrete paxticles having the shape of discs. 2. To model and represent the interaction of interstitial pore fluid present with the idealized granular media. The representation of the solid skeleton is based on Cundall and Strack's distinct element model, in which discrete particles axe modelled as discs in two dimensions, each obeying Newton's laws. Interparticle contacts consisting of springs and frictional element dashpots are included. Assuming a Newtonian incompressible fluid with constant viscosity and density, and quasi-steady flow, the fluid phase is described by Stokes' equations. The solution to Stokes' equations is obtained through the boundary integral element formulation. Several validation test cases axe presented along with four simple shear tests on dry and saturated granular assemblages. For these last four tests, the numerical results indicate that the model is able to represent qualitatively the behavior of real soil, while at the same time clarifying the processes occurring at the microscale that influence soil response.