Geomechanics risk model for multiple failures along rock discontinuities

Abstract This paper is concerned with the risk of slope failure along discontinuities considering the shear strength parameters as random variables. Attention is focussed on planar discontinuities in rock. A risk model for the occurence of multiple or successive failures is presented based on a joint or bivariate probability distribution of the safety margins associated with a pair of discontinuities. The conditional probability of failure along a discontinuity, given that a previous failure has occurred, may be several orders of magnitude greater than the calculated probability considering failure as an independent event. Attention is given to the influence of statistical parameters of shear strength on the probability of failure extending from one slip surface to the next. The importance of accuracy in numerical calculations is emphasized. The implications of various assumptions and the role of novel approaches within a probabilistic framework are discussed.