Triaxial residual strength of an anisotropic rock

Abstract

Peak strength and its failure criteria of anisotropic rocks have been studied and reported. However, few publications referred to residual strength behavior of anisotropic rocks.;A laboratory testing technique, called the multiple failure state of triaxial test, was adopted to evaluate the residual strength behavior of anisotropic rocks in triaxial compression. A series of tests was performed on core samples of argillite. The experimental results show the fact that the triaxial residual strength is directly related to the inclination angle of specimen foliation with respect to the axial loading direction. The minimum triaxial residual strength occurs in the specimen with 30 degrees of inclination angle; and specimens with 0 degrees or 90 degrees inclination have maximum triaxial residual strength. Analyzing the experimental data by the basis of the Mohr-Coulomb failure criterion, the residual cohesive strength strongly depends on the inclination of foliation. Nevertheless, the residual friction angle is independent of the inclination of foliation. A new failure criterion of triaxial residual strength for anisotropic rocks, modified from the Hoek and Brown failure criterion, is proposed in this paper. The criterion correlates closely with the experimental data of argillite specimens and can be extended to estimate the triaxial residual strength for inherent anisotropic rocks with discontinuities.