AVERAGE STRESSES AND FORCE FLUCTUATIONS IN NONCOHESIVE GRANULAR-MATERIALS

A lattice model is presented for investigating the fluctuations in sta tic granular materials under gravitationally induced stress. The model is similar in spirit to the scalar q model of Coppersmith et al. [Phy s. Rev. E 53, 4673 (1996)], but ensures balance of all components of f orces and torques at each site. The geometric randomness in real granu lar materials is modeled by choosing random variables at each site, co nsistent with the assumption of cohesionless grains. Configurations of the model can be generated rapidly, allowing the statistical study of relatively large systems. For a two-dimensional (2D) system with roug h walls, the model generates configurations consistent with continuum theories for the average stresses (unlike the q model) without requiri ng the assumption of a constitutive relation. For a 2D system with per iodic boundary conditions, the model generates single-grain force dist ributions similar to those obtained from the q model with a singular d istribution of q's.