Collapse of a two-dimensional brittle granular column: Implications for understanding dynamic rock fragmentation in a landslide

We investigate numerically the failure, collapse, and flow of a two-dimensional brittle granular column over a horizontal surface. In our discrete element simulations, we consider a vertical monolayer of spherical particles that are initially held together by tensile bonds, which can be irreversibly broken during the collapse. This leads to dynamic fragmentation within the material during the flow. Compared to what happens in the case of a noncohesive granular column, the deposit is much rougher, and the internal stratigraphic structure of the column is not preserved during the collapse. As has been observed in natural rockslides, we find that the deposit consists of large blocks laying on a lower layer of fine fragments. The influence of the aspect ratio of the column on the runout distance is the same as in the noncohesive case. Finally, we show that for a given aspect ratio of the column, the runout distance is higher when the deposit is highly fragmented, which confirms previous hypotheses proposed by Davies et al. (1999).