Improved Strength Criterion and Numerical Manifold Method for Fracture Initiation and Propagation

Abstract

This paper develops a novel empirical strength criterion and proposes a manifold method for fracture initiation and propagation. First, to investigate the influencing factors of fractured rock mass strength, a set of uniaxial and biaxial compression tests were performed on gypsum specimens. According to the experimental results, rock mass strength is attributable to nonlinear relationships with fracture inclination angle, length, and lateral pressure. Then, on the basis of strength theory and tests, an improved empirical strength criterion, which can describe the multi-influence of fracture inclination angle, fragmentation degree, and lateral pressure on strength of the rock mass and the path of fracture propagation, was established. Moreover, the critical conditions of tensile and shear fracture for fracture propagation are proposed and used with a numerical manifold method to simulate fracture propagation. Furthermore, in the modeling, the manifold element is regarded as the basic failure element, and the failure angle is used to determine propagation direction. The results of the fracture-initiation strength and the propagation path with traditional Mohr-Coulomb criterion and the improved empirical strength criterion are compared to validate the proposed method.