A Procedure for Assessing the Orientation of Failure Plane in Transversely Isotropic Rocks

In this work, a novel procedure for assessing the strength and the orientation of failure/localization plane in transversely isotropic rock masses is developed. The specification of a failure plane is required in a broad range of methodologies used for assessing the limit load of geotechnical structures, which include the limit equilibrium approach, the upper bound limit analysis as well as incremental numerical analysis dealing with localization and propagation of damage. The approach employed here incorporates an enhanced analytical form of a Mohr failure envelope corresponding to generalized Hoek Brown criterion. The latter is defined in terms of components of traction vector acting on a plane of a given orientation. The proposed methodology incorporates the critical plane approach in which the strength parameter(s) vary with the spatial orientation of these planes. A comprehensive numerical study is conducted, involving assessment of conditions at failure and the orientation of failure plane in a series of conventional triaxial and true triaxial tests. The results of numerical simulations provide a clear illustration of how the intermediate principal stress and the orientation of fabric influence the failure behavior of rock masses.