An experimental investigation of the fabric effect on angle of repose

Physical model tests have been carried out in this study, to investigate the effect of fabric on angle of repose in granular piles. On the one hand, particles are deposited at various directions when constructing granular piles, to create different fabric characteristics; on the other hand, several leakage holes are set at the bottom of original (mother) granular piles to construct sub-piles (children piles) such that the effect of internal structures of mother pile on angle of repose can be examined. The results show that the angles of repose, alpha and beta, for the mother and children piles, respectively, decrease at first and then increase as the orientation angle theta of deposition plane varies from 0 degrees to 90 degrees, whereas the angle of repose gamma shows an reverse variation trend. Note that the angle regions, where the minimum alpha (or beta) and maximum gamma occur, are complementary, respectively being theta = 30 degrees -45 degrees and theta = 45 degrees - 60 degrees. The analysis of the basis of a conceptual model leads to the finding that the more the deposition plane orientation approximates to the orientation of potential slipping surface, the smaller the angle of repose is, and the more the deposition plane orientation deviates, the larger the angle of repose is. The fundamentals underlying the observation that alpha, beta, and gamma have their maximum or minimum values at special angle regions, are clarified. At last, a disturbance zonal model is proposed to account for the mechanism how the position of leakage holes (i.e. internal structure in mother piles) affects the angles of repose beta and gamma.