Evaluation of Reservoir Slope Stability Considering Friction Angle Uncertainty and Earthquakes

Abstract

Approximately 76% of the reservoirs built in Korea are facilities that are more than 50 years old. The risk of disasters has increased because of reservoir aging and the deepening polarization of drought and floods caused by abnormal weather conditions. In addition, the number of earthquakes has been gradually increasing in Korea, and anxiety has increased significantly because of the recent series of large earthquakes since the earthquakes in Pohang and Gyeongju. Accordingly, risk assessment and preparation are required through the stability evaluation of earthquakes in old reservoirs. The stability evaluation method, based on the limit equilibrium method, depends highly on the soil strength parameters; hence, it is essential to identify the soil strength parameters accurately. However, even though the soil strength parameters are of the same layer, they have different values because of the heterogeneity of the ground. It is difficult to select the representative value of the soil strength parameters because of the time and economic constraints of the ground survey. Therefore, in this study, the probability of failure of an old reservoir owing to seismic events was calculated, and the stability was evaluated. The water level and the uncertainty of the strength constant of the reservoir were considered. The analysis showed that the probability of collapse has increased because of the increase in the water level and the coefficient of variation of the friction angle, and the stability of the reservoir, considering the seismic events, was found to not satisfy the minimum factor of safety for slope activities.