Probing the boundary effect in granular piles

Abstract

We present in this paper a DEM study of the effect of boundary configuration on the formation of granular piles. We examine the macro and micro responses of granular piles formed in a two-wall boundary system consisting of a horizontal base and an inclined wall. The results show that the left inclined boundary wall does not exert a considerable impact on the angle of repose \(\alpha _{R}\) estimated by the right free surface of granular pile, but it has an obvious effect on the angle of repose \(\alpha _{L}\) obtained by the left free surface. We observe the shifting of pile apex to the left inclined wall, with the shift distance depending on the orientation angle \(\beta \) of inclined wall. The principal stress field of granular pile is characterized by two sub regions, in which the major principal stresses are oriented respectively in acute and obtuse angles relative to the horizontal axis. We propose an index \(\lambda \) relating to the distribution of the two sub regions of principal stress field, and identify a relationship between \(\lambda \) (\(=\,\sin \beta \)) and \(\beta \) to account for the effect of boundary configuration on the internal mechanical responses of granular pile. We also analyze the boundary responses at varying \(\beta \) values, and observe three modes for the friction mobilization along the inclined boundary wall, on the basis of which we preliminarily illuminate the effect of boundary configuration on the macro responses of granular piles.