Numerical Investigation on the Mechanical Properties of Australian Strathbogie Granite Under Different Temperatures Using Discrete Element Method

Abstract

A series of laboratory tests was conducted on Australian Strathbogie granite with different grain sizes from fine to coarse, which focus on the influence of temperature on the mechanical properties of the rock. The specimens were compressed under different temperatures, varying from room temperature to 800\xa0°C. A numerical model using Discrete Element Method was proposed to investigate the mechanism of heat-induced fracturing, which could handle both the inter-granular and intra-granular fractures. In the simulation, three kinds of grain sizes with different grain distribution were considered, which are fine grain (FG), medium grain (MG) and coarse grain (CG). All FG, MG and CG models were performed using the same set of strength and stiffness parameters. It was found that the outcome of the numerical model had a good consistency with the results from the compressive tests, both in strength and deformation. The compressive strength of granite showed decreasing trends with increasing temperature, while failure strain showed the opposite trends. The temperature induced fractures increased quickly as temperature increased especially when temperature was above 400\xa0°C and the fractures were mainly inter-granular tensile ones. The intra-granular fractures began to appear as the temperatures were over 400\xa0°C. As for grain size homogeneity, the compressive strength decreased as the heterogeneity of granite grains increased. The heterogeneous granite had more intra-granular fractures than uniform granite at high temperatures.