Numerical and experimental investigations of grain size and temperature effects on the crack propagation velocity in brittle rocks

Abstract

Understanding the behavior of rock failure under the influence of grain size and temperature is a critical topic in rock mechanics due to its complexity and significance. The impact of these factors, particularly on crack initiation and propagation processes, is a complex and multifaceted issue that has been the focus of engineering rock studies. These effects are especially noticeable when temperature changes drastically, such as deep mining projects or construction in high-temperature regions. Based upon the distinct element method (DEM), this study used the particle flow code (PFC) to numerically simulate the rock fracture process under three-point loading on semi-circular bending (SCB) specimens. A total of 96 fracture toughness tests were simulated on samples with grain sizes of 0.5, 0.75, 1, and 1.5 mm at temperatures ranging from 25 to 700 °C and under mode I, mode II, and mixed-mode fracture loading conditions. The numerical models were validated against uniaxial compressive strength and Brazilian tensile strength test results. This study uniquely examines how temperature and grain size affect crack propagation velocity across different loading conditions. The findings showed that, as temperature increases, microcracks lead to thermal expansion in the samples, and the crack propagation velocity also increases. Additionally, there is an inverse relationship between grain size and crack propagation velocity. Notably, the results showed that the effects of grain size and temperature on crack propagation velocity vary across different fracture modes.