Numerical approach to influence of heterogeneity on failure process of Brazilian disk of rock

The behavior of a specimen under uniaxial tension and the process of microfracture in such a specimen are phenomena of considerable interest from the point of view of understanding strength charaterization of rock. We present numerical results, based on A simulator named Rock Failure Process Analysis code (RFPA), that show the nucleation and growth of macrocracks in relatively homogeneous and heterogeneous specimens under uniaxial tension. In this simulator, the heterogeneity of rock is considered by assuming that the material properties of elements conform to Weibull distribution, an elastic damage-based law that considered the strain-rate dependency is used to describe the constitutive law at mesoscopic scale, and finite element program is employed as a basic stress analysis tool. The failure process of Brazilian disk of rock is numerically simulated, and the numerical results are compared with the available experimental results. While the details of macrocrack formation varied from specimen to specimen, a number of features were consistently obtained in the numerical simulations. In all relatively homogeneous specimens, the macrocrack nucleated abruptly at a point in the specimen soon after reaching peak stress. Prior to macrocrack nucleation, AE events or microfractures were distributed diffusely throughout the specimen. It is very difficult to predicate where the macrocrack will initiate. The failure of the specimen is completely brittle and no residual strength is observed. Relatively heterogeneous specimens showed somewhat different response. In these simulations, the same diffused AE events or microfractures but with higher count number appeared in the early stage of loading. For the specimens with the same property of heterogeneity, however, the numerical simulations show that the failure modes depend greatly on the crack initiation location that is found to be sensitive to the local disorder features within the specimen.