A method for distinguishing between single and double plane sliding of tetrahedral wedges

A simple rule to distinguish between single and double plane sliding of tetrahedral wedges, assuming only body forces and hydrostatic forces are acting, is presented. This rule differs from that given by panet, who assumed that the analysis was independent of the orientation of the slope face for the plane sliding case; this assumption is shown to be incorrect. The distinction between single and double plane sliding is important; if sliding down the line of intersection is always assumed, then the stability of the wedge will be overestimated for cases in which sliding down a single plane actually occurs. /TRRL/