Three-dimensional DEM investigation of the fracture behaviour of thermally degraded rocks with consideration of material anisotropy

Abstract A complete understanding of the fracture behaviour of anisotropic rocks under elevated temperatures is fundamentally important for rock and reservoir engineering applications. This paper shows a three-dimensional numerical investigation of the fracture behaviour of anisotropic sandstone, with consideration of the effects of temperature and material anisotropy. In the study, a 3D semi-circular bend (SCB) model was established by using the Discrete Element Method (DEM). The thermal responses of different minerals and the strength anisotropy of incipient bedding planes were considered in the model. The DEM model was calibrated against a series of laboratory experiments on Midgley Grit sandstone (MGS) that exhibits intrinsic anisotropy. The pure mode I, mode II, and mixed-mode (I+II) fracture characteristics of the MGS were investigated under elevated temperatures (up to 600 °C) using the established DEM model. The thermal degradation (i.e., fracturing) of the rock, the fracture load, the evolution of micro-cracks, and the stress-strain relationship around notch tips were analysed, with emphasis on enlightening the micro-mechanisms underlying the fracture behaviour. The results of the study were discussed and then compared with experimental observations and theoretical predictions.