Experimental analysis of scree slope behaviour: The influence of particle morphology

This study conducts a series of physical model tests to investigate the effect of particle morphology on the scree slope characteristics which mainly refer to the particle sorting and slope angle. Granular-mixture release tests show that the greater the morphological disparity — i.e., the differences in particle size and shape—between two constituent materials, the more prominent the particle sorting becomes. The sorting degree increases with the relative particle size and shape factors (SF_r and OR_r). A larger size disparity tends to result in a smaller slope angle and a more stable structure, while a greater shape discrepancy leads to a larger slope angle and a less stable structure. Single-particle release tests indicate that large, regular-shaped particles tend to travel farther, whereas small, irregular ones travel less. Compared to deposits of regular-shaped particles, deposits of irregular-shaped particles exhibit a higher resistance to impact and a lower energy absorption capacity due to a less notable impact deformation, allowing released particles to retain more kinetic energy and move further. Conceptual models are proposed to illustrate how particle morphology influences particle sorting from the perspective of particle motion. The influence of particle morphology on slope angle is further explained through its effect on the packing state and interlocking of deposited particles. Finally, a correlation between particle sorting and maximum slope angle is explored via a new concept of relative flowability, defined as the ratio of the angle of repose between constituent materials.