Effects of the size polydispersity and friction coefficient on the compressive strength of wet granular materials

We numerically study the effects of the size polydispersity and the friction coefficient on the compressive strength of wet granules under a diametrical compression test by using discrete element simulations. The nu-merical method is coupled with the capillary cohesion law which is enhanced by the cohesive forces between grains in the pendular regime. The wet granules are composed of primary spherical particles whose size poly-dispersity is varied from1 to 10 and the friction coefficient between grains is varied from0.1 to 1.0. By applying a constant compression velocity on the top plate in quasi-static regime, the granule is deformed but does not abruptly rupture due to the cohesive effects between grains and the rearrangement of primary particles. This no abrupt rupture is characterized by the appearance of the peak compressive stress in a long vertical strain before the onset failure of the granule. The compressive strength of the granule increases with increasing the friction coefficient for all cases of the size polydispersity but seemly declines for low values of the size polydispersity and almost level-off for high-size polydispersity with the friction coefficient larger than 0.5.