Stability and Evolution of Planar and Concave Slopes under Unsaturated and Rainfall Conditions

Natural slopes are often observed to have a concave, convex, or a combination concave/convex profile, yet constructed slopes are traditionally designed with planar cross-sectional geometry. In this paper, the stability of two planar slopes was compared with that of companion concave slopes, designed to have similar factor of safety (FOS) under gravity loading. The stability of these slopes was then investigated in response to a suction event followed by a precipitation event, and it was shown that both the planar and the concave slopes experienced similar changes in stability. Additional analyses were conducted with a simulated erosion mechanism to investigate how the planar and concave shapes would evolve under a sequence of three similar suction/precipitation/erosion cycles. The results suggest that for these slopes, the second and third simulated weather cycles reduced the stability of the slopes, yet had a lesser effect on the concave slopes than the planar slopes. This is in spite of the fact that the planar slopes became more concave-like due to the simulated erosion and suggests that slopes designed to be concave may perform better than the planar slopes.