A case study of failure mechanism and support measures of slopes against sliding and toppling failure

Stability analyses were carried out to confirm the stability of the G2M slopes of the Karun 3 Dam Hydro - Electric Power Project (HEPP), located southwest of Iran. The slopes above the Take off Yard were exhibiting significant movement especially during the rainy seasons. It was deduced that the movement is a combination of flexural toppling in the lower levels and planar/block sliding at the upper levels of the slopes under study. The stability analyses were performed by the limit equilibrium method leading the need and volume of the protective measures to stabilize the whole slopes mass. The various stabilization methods such as unloading by benching, drainage, and rock bolting were investigated and it was decided to apply a combination of all. Based on the analytical studies, the surface weathered mass was removed and the excavation of the benches was undertaken as per the design. Prior to the surface excavations, the drainage gallery and the related fan holes were completed. The rock bolting was done concurrent with the surface excavations. The details of the failure mechanism, monitoring system, stability analyses, and application of the protective measures are given in this paper.