Shear flow of dense granular materials near smooth walls. II. Block formation and suppression of slip by rolling friction

Abstract

The role of rotational degrees of freedom and of microscopic contact properties at smooth walls in two dimensional planar shear has been investigated by contact dynamics simulations of round hard frictional particles. Our default system setup consists of smooth frictional walls, giving rise to slip. We show that there exists a critical microscopic friction coefficient at the walls, above which they are able to shear the granular medium. We observe distinctive features at this critical point, which to our knowledge have not been reported before. Activating rolling friction at smooth walls reduces slip, leading to similar shear behavior as for rough walls (with particles glued on their surface). Our simulations with rough walls are in agreement with previous results, provided the roughness is strong enough. In the limit of small roughness amplitude, however, the distinctive features of shearing with smooth walls are confirmed.

Numerical investigation of the interplay between wall geometry and friction in granular fault gouge

“…The wall offsets at the boundary the granular shear with values of μ wall controlling the amount of offset. At extremely low μ wall and an infinitely smooth wall, no shear occurs in the granular layer [ Shojaaee et al ., ]. Shojaaee et al .…”

“…Both da Cruz et al . [] and Shojaaee et al . [2012] find that 〈μ macro 〉 increases with increasing I over many orders of magnitude, the velocity‐strengthening situation.…”

“…Shojaaee et al . [] simulated 2‐D disks between infinitely smooth walls and vary both μ particle and μ wall . Their results quantitatively agree with our simulations that 〈μ macro 〉 becomes insensitive to μ particle at values ~0.7.…”

“…Shojaaee et al . [] find that, as the wall roughness increases, frictional strength of the system increases and eventually becomes independent of roughness, agreeing with our simulations (Figure a).…”

Unsteady granular flows down an inclined plane

“…Neither of the approaches has established analytical forms of velocity and stress profiles, which are required to access energy dissipation, or the associated destructive potential of the flow. In addition, friction coefficient is known from physics and geophysics to depend on shear rate or relative sliding velocity between two surfaces [6][7][8][12][13][14]. Knowledge of shear rate could thus facilitate development of theoretical friction models.…”