Numerical Simulation of a Ciclically Loaded Granular Soil Using the Discrete Element Method

In order to evaluate numerically the liquefaction potential of granular soils, several simulations were performed, using the Discrete Element Method (DEM), Cundall & Strack (1979), of different assemblies of spherical particles under periodical boundary conditions (PBC). To perform the simulations, the open source and free license software YADE (V. Smilauer, E. Catalano, B. Chareyre, S. Dorofeenko, J. Duriez, A. Gladky, J. Kozicki, C. Modenese, L. Scholtes, L. Sibille, J. Stransky, and K. Thoeni, Yade Documentation, The Yade Project, 1st ed., 2010.) was employed. A modified Cundall-Strack law, with cohesion and torque at the contacts, was established between particles, being the only interaction defined, due to the lack of physical walls or boundaries. All the particles were spherical, and different grain size distributions (GSD) were tested. The main objective of the simulations was the study of the influence of the relative density (RD) and uniformity coefficient (UC) on the liquefaction resistance of the granular assembly. To achieve this goal, several consolidated-undrained cyclic triaxial tests were simulated, under strain controlled conditions. The numerical tests were performed in three dimensions (3D), without interstitial water. To simulate the undrained condition of the test and to assess liquefaction, the volume of the assembly was kept constant during the cyclic loading phase, and the pore pressure was computed as the normalized difference between the total stresses developed and the confining pressure applied. The results of the numerical simulations performed are presented and analyzed, and conclusions are drawn about the influence of the RD[%] and UC on the liquefaction resistance of the granular assemblies.