The failure process of Hong Kong granite under uniaxial compression has been numerically investigated and simulated at mineral grain level based on RFPA (Rock Failure Process Analysis) code. For better understanding the parameters used to describe the failure properties of minerals, a systematic analysis on the corresponding parameters, especially the homogeneity index (M) and the ratio of compressive strength to tensile strength (C/T), had been firstly carried out. According to the analysis results and the facts observed experimentally, a set of parameters was then obtained, which could well reproduce the actual process. It is found from our simulation study that under uniaxial compression the significant cracking of granite begins with the obvious cracking of quartz. The nonlinear behavior of granite prior to the peak-point seems to be closely related to the quartz failure, whereas feldspar appears to act as a dominant mineral phase to determine the failure behavior of granite in post-peak region. Higher crack density around biotite grains is mainly caused by great difference between biotite and neighboring minerals in modulus.
The failure process of rocks, especially brittle rock such as granite, is difficult to trace experimentally. It is not only because they usually fail suddenly but also because some specific techniques are often required, so that the numerical approach is more popular in this research field. The powerful capacities of failure visualization, repeated test and easy operation make it greatly useful to represent the physical process and to reveal the failure mechanisms. A lot of numerical simulation investigations concerning the failure of granite had been carried out based on different models and by employing different methods (Hashida et al, 1993; Liu et al, 1997; Tan et al, 1997; Homand-Etienne et al, 1998 and Kelner et al, 1999). However, simulation studies regarding the failure of minerals containing in granite are very few. As granite is a complicated polycrystalline material, the failure process is apparently related to the failure behaviors and failure mechanisms of the minerals. It is, therefore, important to study such process at this micro level. The present investigation intended to reveal the roles of different minerals in granite during the failure process and to simulate this process numerically by using RFPA (Rock Failure Process Analysis) code. The RFPA was developed in the Center for Rockbursts and Induced Seismicity Research, Northeastern University, China, and had been successfully applied in various rock mechanics problems (Tang, 1997; Kaiser et al, 1998; Tang et al, 1998a; Tang et al, 1998b and Tang et al, 1998c). The detailed description about this two-dimensional code was reported by Tang (Tang, 1997). It is found from our investigation that the simulation results can reproduce most of the observable characteristics of the actual failure process and several new findings have been obtained, which are important for better understanding the failure mechanism of granite.
To perform a micro failure simulation, the different mineral phases in the rock material have to be considered at mineral grain level.
