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Microwave irradiation has been considered a promising solution for high-temperature cracking rock. Most of the current researches are concentrated on investigating the effects of microwave irradiation on the physical and mechanical properties of rock. However, there is a paucity of reports on the application of microwave irradiation for controlling rockburst disasters. The novelty of this investigation lies in the utilization of microwave irradiation to modify the energy storage capacity and fracture characteristics of brittle rock with rockburst proneness. Based on the phenomenon of overheating in rock under microwave irradiation, the concept of progressive damage in granite was proposed for the first time. The weakening of energy storage capacity due to microwave irradiation was evaluated by defining an energy storage coefficient. A novel index for assessing the rockburst proneness of brittle rock was proposed. By combining this index with the strain energy release rate, the potential value of microwave irradiation in reducing the proneness and intensity of rockburst was explored. This study also introduced the concept of ''sensitive stress level'' which influences the closure state of cracks, and found that SSL and mechanical properties show high sensitivity to microwave power. A threshold power of 4.5 kW was identified, at which numerous parameters undergo significant changes.

Abstract The crack propagation behavior of rock during compression involves complex mechanisms. Describing the growth behavior of a large number of cracks with conventional mechanical models is a major challenge. Therefore, in this work, we propose a new method to describe crack growth behavior by considering crack bodies as free voxels that can expand and coalesce within a rock sample according to certain rules. Specifically, we first propose a crack growth model that quantitatively describes the crack growth ratio and crack growth rate, which are integrally related to the loading rate, internal friction angle, cohesion, initial porosity, and confining stress. Second, to avoid the complex analytical process of the traditional mechanical model in solving the propagation directions of multiple cracks, we introduce a method for determining the crack growth directions of shearing failure based on the colony growth assumption. This method defines the crack propagation direction as a synthetic vector of the inertial direction, the attractive direction, the Coulomb direction, and the edge direction. Moreover, a new mathematical description method of fracture energy and plastic energy is proposed to calculate the crack growth at each time step. The simulation results show that our crack growth model for shearing failure agrees well with the experimental results and explains the fracture behavior and transformation law of cracks to some extent.

The surrounding rock in tunnelling engineering and coal mining will sometimes be exposed to high temperature. Rock failure is the result of energy dissipation, and the study of the evolution and transformation behavior of energy is of great significance for the in-depth understanding of the deformation and failure of rock after high temperature. This study analyzed the intrinsic connection between mechanical properties and acoustic emission (AE) energy under temperature effect. Based on the energy dissipation and release theory, the distribution and transformation of energy was analyzed, and the energy self-incentive and self-inhibition (EII) model was further established. The main findings are that temperature effect affects the confidence interval trend and the value of AE energy rate, which is related to the change in mechanical properties. The ability of sandstone to store elastic strain energy after exposure to high temperature is independent of the mechanical properties. In this study, the ratio of dissipated energy to elastic energy is used to characterize the stable state of the sandstone system, which can be used as the energy indicator of rock failure precursor. During the absorption, storage, and release of energy before the peak stress, there exists self-incentive and self-inhibition of energy (control behavior).

High energy consumption in ore crushing brings great challenges to the mining industry. Microwave irradiation provides a promising solution for rock breaking. However, there is currently a lack of detailed understanding of the microwave parameters regarding magnetite ore. The purpose of this study is to fully understand the potential value of microwave irradiation applied in auxiliary crushing of magnetite ore. It is typically found that increasing power reduces the mechanical properties of ore, increasing energy utilization, and crushing degree, more than extending time. Based on wave impedance, this reveals the dependence of energy utilization on thermal damage. Increasing irradiation power, time and cooling rate will cause more transgranular cracks and cleavage tears in the crushed ore. Based on the separate microwave response of several minerals, the microwave-damage mechanism of magnetite ore is further demonstrated.