An efficient approach for stability analysis of rock slopes subjected to a transient drawdown

Since the water drawdown in a reservoir easily triggers the instability of a nearby slope, chart research on slopes that are subjected to drawdown conditions has attracted extensive attention recently. However, most studies only consider the extreme 'rapid/slow' drawdown conditions and ignore the general 'transient' drawdown scenario. This paper proposes an efficient approach for stability analysis of rock slope subjected to a transient flow, and provide a chart study and a parametric analysis. To address the challenge of determining the bent phreatic surface in a transient flow and to employ the nonlinear Hoek- Brown criterion of rock masses, a phreatic equation was adopted in this paper, together with the discretization technique. In the framework of limit analysis, the external work rate and the internal energy dissipation rate were computed. A calculation flow was proposed for capturing the optimized factor of safety (FOS) based on the strength reduction technique. Then, following the evaluation of this approach, a set of stability charts and an application example were presented. A parametric analysis was conducted to evaluate the influences of the rock properties and the hydrodynamic parameters on the factor of safety.