Stress distribution in static two-dimensional granular model media in the absence of friction

We present simulations of static model sandpiles in two dimensions (2D), and focus on the stress distribution in such arrays made of discrete particles, We use the simplest possible model, i.e., spherical particles with a linear spring and a linear dashpot active on contact and without any frictional forces, Our model is able to reproduce several recent theoretical predictions. For different boundary conditions we examine the contact network and the stresses in the array and at the bottom of the pile. In some cases we observe a dip, i.e., the relative minimum in pressure, under the center of the pile. We connect the dip to arching, and we relate arching to the structure of the contact network. Finally, we find that small polydispersity is sufficient to cause a so called stress network, i.e., strong fluctuations in stress. From these data we determine the probability distribution for the vertical stress at the bottom, and relate it to theoretical and other numerical work.