Mechanical behaviour of Lac du Bonnet granite after high-temperature treatment using bonded-particle model and moment tensor

Abstract

The thermal cracking mechanism has been increasingly investigated to analyse and solve the mechanical behaviour of rocks in deep underground engineering. Classic laboratory tests bear the intrinsic limitation of non-repeatability and lack of direct observation of the interaction effect between thermal stresses and thermal micro-cracks. In this paper, the bonded-particle model and moment tensor is used to simulate the process of thermally induced micro-and macro-cracks in Lac du Bonnet granite to help provide insight into the detailed influence temperature on mechanical properties and acoustic emission characteristic of granite. During modelling, macro- and microscopic responses are quantified and compared against other laboratory data in the literature. The results indicate thermal stresses and thermally induced micro-cracks increase with increasing temperatures during heating, and cooling generally reduces the thermal stresses and increases the micro-cracks slightly. Grain-size distribution has a significant influence on thermal micro-cracks, thermal stress and the mechanical behaviours of granite. The increase in thermally induced tensile intergranular micro-cracks density mainly contributes to reduction of mechanical properties in granite samples subjected to heating–cooling cycles. It is also observed that the nature of sources and the b-value are associated with temperature, which gives some light on underground engineering in high temperature environments.