ABSTRACT
The above mentioned studies successfully predict the failure process in one aspect or another but they have limitation as well. For example, in the application of fracture mechanics theory, it is difficult to estimate the micromechanical parameters such as crack density and toughness for cracks in different modes. Continuum modeling based on grid base methods sometimes do not work well for the simulation of failure process involving large deformation and fragmentation. Another method
1 INTRODUCTION
The prior information regarding the failure pattern of geomaterial is a major concern in various excavations made in soil or rock viz. tunnels, slopes and mining excavations. Over the past several decades, researchers have performed numerous experimental studies on various type of rock material and provided explanation of failure mechanism according to their observed strength and failure behavior of the material (Sprunt & Brace 1974, Wong et al. 1996) study. Their investigations have revealed that the macroscopic behavior and the failure process are generally initiated by the microcracks development, propagation and interaction of several cracks, defects and inherent flaws. The mechanical properties and the failure characteristics of rock are sensitive to loading rate and rock sample undergoes through multiple physical processes which occur at the different time and length scales. A circular disk type rock sample under angular concentrated load generally fails along the loading axis due to tension generated at the middle of the sample.
