Instabilities in rock masses like jointed rock slopes, involve coupled mechanisms related to both deformations along pre-existing discontinuities and fracturing of intact rock. Back analyses of slope failures have shown that the breakage of intact rock bridges located in the vicinity of the pre-existing discontinuities plays a critical role on the process of destabilization and strongly influences the development of the final failure surface. Mass strength degradation and progressive failure mechanisms in these intact rock bridges cannot be ignored and must be considered to predict the overall stability of a rock mass.
The Discrete Element Method (DEM), which enables to describe highly non-linear behaviors characteristics of geomaterials, constitutes an efficient tool to simulate the irreversible processes taking place in rock during loading. The DEM provides a description of the localized stress-induced damage caused by heterogeneities that are inherent in rocks and is able to reproduce the progressive mechanisms leading to failure; from the initiation to the propagation and possible coalescence of cracks occurring at the microscale.
An enhanced version of the DEM has been specifically developed for the analysis of jointed rock masses stability. In addition to the discrete representation of the intact medium, structural defects can be explicitly taken into account in the modeling to represent pre-existing fractures or discontinuities. From laboratory scale simulations to slope stability case studies, the capability of this approach to simulate the progressive failure mechanisms occurring in jointed rock are presented on the basis of referenced experiments and in situ observations.
For instance, the challenging wing crack extension, typical of brittle material fracturing, can be successfully reproduced under both compressive and shear loading path, as a result of the progressive coalescence of micro-cracks induced by stress concentration at the tips of pre-existing fractures.