Bonded-particle discrete element modeling of mechanical behaviors of interlayered rock mass under loading and unloading conditions

Interlayered rock mass composed of green schist and marble is widely observed in China, such as the Jinping II hydropower project site in Sichuan Province. Its mechanical behaviors are of importance for the overall project stability. Unfortunately, for most cases, field or laboratory tests seeking to truly represent the mechanical behaviors of interlayered rock mass under dynamic loading condition is very difficult. In order to understand its mechanical performances under loading and unloading conditions, a numerical modeling was conducted to analyze its mechanical characteristics using soft package PFC2D. The numerical results show that (a) the inclined angle of interlayered rock mass has a major effect on the strength of rock specimen under triaxial compression loading, and the minimal compressive strength was generally observed at an orientation angle of 30 degrees-45 degrees. However, the influence of marble component on the strength of interlayered rock mass is not clear when the inclined angle is in the range of 30 degrees-45 degrees. (b) When neither the confining pressure nor the marble composition is varied, few cracks were generated at inclined angle of 45 degrees than that at other angles under triaxial compression loading condition, and the micro-crack is basically characterized by shearing failure. (c) When the inclined angle increases from 0 degrees to 90 degrees, the minimum principal stress increases first and then decreases under unloading confining pressure, and the minimum principal stress reaches peak at an inclined angle of 45 degrees. (d) Crack development and failure mode of interlayered rock mass are mainly influenced by the rock material properties, particles arrangement and rock layer distribution, whilst the stress path has no effect on crack development and failure mode of interlayered rock mass.