Progressive deterioration and fracture mechanisms of heterogeneous rocks induced by open-ended microwave irradiation: A multi-scale numerical and experimental investigation

A comprehensive multi-scale spatial investigation of the time-dependent process of microwave-irradiated rock is conducive to revealing its underlying failure mechanisms. The innovation of this study lies in the systematic analysis of the progressive failure process of heterogeneous rocks induced by open-ended microwave irradiation, from temporal-spatial and multi-scale. Based on a high-fidelity heterogeneous rock model, a time-stepping iterative staggered finite element approach is proposed for solving multi-physical processes. And the process from local deterioration to global fracture of the rock under microwave irradiation is simulated. The results indicate that the failure process can be divided into three stages: Non-failure Stage (NFS), Local Deterioration Stage (LDS), and Global Fracture Stage (GFS), with the evolution characteristics significantly influenced by the rock structure and microwave conditions. The increase in microwave power and the associated thermal shock effects not only weaken the uniaxial compressive strength of the rock, but also accelerate the onset of LDS and GFS, while shortening the duration of LDS. The meso-mechanical analysis reveals that the local high tensile stress at the grain boundaries makes these regions more prone to failure than the interior of the grains, with biotite and feldspar grains being more likely to fail. Additionally, the marked crack path trajectories show that the low proportion of biotite and the high strength of quartz jointly influence the crack propagation path. This study provides a multi-scale perspective to reveal the characteristics of microwave-induced rock failure, and can offer guidance for the subsequent timing and path planning of mechanical tool penetration.