A Virtual Crack-Based Numerical Manifold Approach to Crack Initiation, Propagation and Coalescence in Granite

Crack initiation, propagation, and coalescence are important for the understanding of rock mass behavior. In this paper, we use an improved numerical manifold method (NMM) that can stimulate the initiation, propagation, and coalescence of many cracks simultaneously to model the continuous–discontinuous deformation of granite under uniaxial and confined compression. This new simulation method couples subcritical crack growth (SCG) theory and the Mohr–Coulomb strength criterion with tension cut-off to consider the propagation of virtual and real cracks, respectively, and uses a statistical Weibull distribution to study the influence of elastic modulus inhomogeneity on crack propagation and rock failure. The mechanical behavior and failure modes of the models are in good agreement with experimental data. Increasing elastic modulus inhomogeneity decreases strength and the strain required for macroscopic failure. The stress corrosion index (n) and crack growth constant (C) also have a strong influence on uniaxial compressive strength. Indeed, higher values of C and n result in faster virtual crack speeds, a lower uniaxial compressive strength, and a lower axial strain upon failure. Confining pressure also exerts an influence on crack propagation, compressive strength, and failure mode. Our study shows that the improved NMM code combined with the virtual crack model is therefore an effective and reliable method to simulate crack initiation, propagation, and coalescence in granite under uniaxial and confined compression.