Strength behaviour of anisotropic rock under true triaxial stress state

Abstract

Strength and deformation behaviour of the isotropic rock under triaxial stress state has been studied extensively, but the studies on the behaviour of the anisotropic rock under true triaxial stress state are scant. The experimental study conducted on the anisotropic rocks are not conclusive due to limited experimental data. In reality, construction of any underground opening results in the application of true triaxial stress state on surrounding geomaterial even the isotropic rocks behave anisotropically due to the presence of the geological structures. In this study, a theoretical strength criterion is proposed for anisotropic rocks and jointed rock mass. The proposed criterion is an extension of Jaeger two-dimensional (2D) anisotropic criterion into three-dimension (3D) using Mogi-Coulomb strength criterion. It is concluded from the study that the most critical anisotropic plane is at angle β = (45+ϕ/2)ο and ω = 90ο. For all the other orientations, the strength is observed to be more than this critical orientation. It is also observed that intermediate principal stress enhances the strength and its influence on foliation or joint is negligible when its orientation is perpendicular to the foliation or joint plane. © 2018 ISRM & SRMEG (Singapore)