Reliability Analysis of an Earth Dam Under Rainfall Effects

Climate change with extreme hydrological conditions, such as extreme rainfall, poses new challenges to earth dam safety. Reliability analysis helps to reduce the uncertainty of the real behavior of a dam, and provides one more tool to improve dam safety control. Reliability analysis is very important for unsaturated soil dams under rainfall conditions. This paper investigates the safety of an earth dam over time, considering different initial conditions, rainfall intensities, and normal operating conditions (NOC). A direct coupling (DC) method is used to integrate different software. Coupling enables us to use the deterministic software packages Seepage/W and Slope/W with the StRAnD reliability software to perform the numerical investigation. The reliability analyses are performed employing the first-order reliability method (FORM) using the improved Hasofer-Lind Rackwitz-Fiesler (iHLRF) algorithm of optimization. The contribution to failure probabilities of random parameters was analyzed with sensitivity analysis. The saturated hydraulic conductivity (k_s) contribution increases when the rainfall intensity increases and when NOC increases or decreases the reservoir. Finally, a critical deterministic slip surface is shown to be very close to the probabilistic one, but a high difference in terms of pore water pressures is reported.