Evaluation of Failure Probability of Old Reservoirs Considering Changes of Strength and Water Level

Abstract

Old reservoirs denote the structures older than 50 years after their complete construction. These reservoirs suffer from both the decrease in stability and the high failure possibility by a hazard. Recently, heavy rain and earthquake have increased the failure possibility of old reservoirs. Thus, it is necessary to prevent the risks by proactively examining the stability of old reservoirs. The limit equilibrium method highly depends upon the soil-strength parameters, and the accurate estimation of soil-strength parameters at the site is essential. However, both economic and time-related limitations cause the uncertainty of soil parameters, thereby making difficult the accurate stability assessment of old reservoirs. Therefore, this study evaluated the stability of old reservoirs and assessed the quantitative probability of failure by using the probabilistic analysis, considering the variation in soil-strength parameters and various uncertainties. As a result of the analysis, it was observed that the probability of failure increases with the coefficient of variation (COV) of both the cohesion and the friction angle. Furthermore, it was confirmed that the COV of the friction angle had a greater influence on the probability of failure than that of the COV of cohesion. Keywords: Old Reservoirs, Seepage Analysis, Slope Stability Analysis, Coefficient of Variation, Probability of Failure