Shear stress and pressure of a granular system with pins

Granular media are large collections of disordered macroscopic particles interacting via dissipative and frictional forces. We encounter them everyday in the shapes of sand, gravel, grains, foams, and even biological beings like bacteria colonies and human crowds. Our research focuses on the effects of pins, small particles that act like restraints, on "jamming", a phase transition when granular media shift from a fluid-like state to a disordered-solid state. Our system contains three types of athermal, bidisperse, repulsive disks in two dimensions with ratio 0.004 (pins) : 1.0 : 1.4 . A shear is applied by moving the top and bottom walls, made of rough particles. We study macroscopic properties such as shear stress, and pressure as function of time and packing fraction and for various shear rates.