Probabilistic analysis of underground excavation stability

Abstract The deterministic description of rock excavation stability with a safety factor is frequently insufficient and, sometimes, misleading. The applications of the probabilistic analysis to determine the likelihood of a rock excavation failure have been proposed by many researchers. The probabilistic analysis will lead to a better understanding of excavation stability and provide more complete information. The difficulty in estimating the failure probability of a underground excavation is the complexity of mathematics involved. In order to overcome this limitation, the first-order second-moment approximation of the failure probabilities is utilized. The technique simplifies the computation significantly and allows for the analysis of relatively complex stability problems. Two underground excavation stability problems are investigated in the study, including the stability of a horizontally layered rock roof and the stability of a underground rock prism. The study indicates that the distributions of parameter values play a significant role in the excavation stability, which can not be disclosed by the conventional methods of stability analysis. Greater dispersiveness of the parameter values will lead to a different probability of failure, although the factor of safety estimated by conventional methods remains the same if the mean values of the parameters are unchanged.