discrete element modeling of drained triaxial test: flexible and rigid lateral boundaries

In the present paper, drained triaxial test on granular materials is simulated by discrete element method. two types of boundary conditions including rigid and flexible boundaries are modeled in the tests. to simulate flexible boundary condition, a new algorithm based on linking the matlab and pfc3d codes is proposed. in this algorithm, triaxial test samples are simulated in pfcd3d and the spatial coordinates of particles are transferred to matlab code. then, boundary particles are identified by irradiation from centerline of specimen and their identities are transferred back to pfc3d to impose boundary forces. the presented algorithm is relatively simple and there is no need of tessellation at the boundary surface. besides, employment of matlab code improves the efficiency of computations. imposition of confining pressure via normal forces to the outer surface of boundary and precise identification of boundary particles in large deformation are other advantages of the proposed algorithm. after validation of the proposed algorithm by some experimental tests, a comprehensive survey has been performed on micro- and macro-behavior of samples simulated by rigid and flexible boundaries.