Stress-dependent anisotropy index of strength and deformability of jointed rock mass: insights from a numerical study

Understanding the anisotropic behavior of jointed rock mass subjected to various confining pressures is crucial for designing, evaluating the performance and assessing the stability of rock engineering structures. We report here our numerical investigation of the response of stress-dependent anisotropy of a jointed rock mass sourced from the weakly weathered zone of the water inlet slope of the Xiaowan Hydropower Station, China. The finite element method (FEM) that incorporates material heterogeneity and joint network was utilized. Two-dimensional models were established based on the Monte-Carlo method and loaded in different rotational angles with changing confining pressures at the representative elementary volume (REV) size (14 × 14 m). The stress–strain behaviors, failure patterns, deformation modulus and peak strength of the REV models exhibited noticeable stress dependency and directionality. The cohesive strength was anisotropic, whereas there was only an insignificant change in the friction angle with changes in the rotational angle. The effect of confining pressure on the anisotropy index of the deformation modulus was negligible, while the anisotropy index of peak strength decreased gradually with confining pressure. Based on these results, we conclude that stress conditions need to be considered for accurate prediction of the mechanical behavior of a jointed rock mass.