Determination of the mixed mode I/II fracture characteristics of heat-treated granite specimens based on the extended finite element method

Previous researches mainly concentrate on investigating the mixed mode I/II fracture characteristics of heat-treated rocks through laboratory tests. This paper makes an effort to obtain the mixed mode fracture characteristics of heat-treated granite by means of the extended finite element method (XFEM), which is based on the cohesive zone model (CZM). The experimentally obtained unstable fracture toughness, tensile strength and tensile elastic modulus of the granite after being subjected to different high temperatures are integrated into the numerical simulation models to estimate the fracture behaviours of the cracked straight-through notch Brazilian disc (CSTBD) specimens under mixed mode loading. Findings and observations from this study indicate that by applying the unstable fracture toughness as the mode independent cohesive zone fracture parameter into the numerical models, although some limitations still exist, the numerical models can successfully predict the fracture loads and the crack propagation paths of the CSTBD specimens under mixed mode loading within the temperature range of 25-600 degrees C. This paper provides a numerical approach to investigate the mixed mode I/II fracture characteristics of thermally treated rocks.