Effect of microwave irradiation on thermal damage behavior of granite: Uniaxial compression test and finite-discrete approach

Abstract

Microwave-assisted rock-breaking technology, as a novel hybrid approach, is anticipated to facilitate the efficient excavation of complex rock formations. It is therefore crucial to understand the damage and failure mechanisms of rocks that have been subjected to irradiation. In this study, uniaxial compression experiments were conducted on granite specimens after 1.4 kW microwave irradiation for varying durations. Furthermore, a numerical method was proposed to solve electromagnetic-thermal-mechanical coupling problems by integrating finite and discrete elements. The results demonstrated a differential temperature distribution (high temperature in the middle and low-temperature areas at the ends) in the granite specimens under microwave irradiation, which resulted in a notable reduction in their physical and mechanical properties. As the duration of irradiation increased, the rate of heating and the extent of strength reduction both diminished, while the morphology and distribution of cracks at ultimate failure became increasingly complex. The numerical method effectively addresses the simulation challenges associated with the electromagnetic selective heating of granite containing multiple polar minerals under microwave irradiation. This approach accounted for the non-uniform thermal expansion of the minerals and provided a comprehensive model of damage progression under compression.

Keywords

• Microwave-assisted rock breaking
• Granite
• Electromagnetic-thermal-mechanical (ETM) coupling
• Finite-discrete approach
• Three-dimensional (3D) grain-based model (GBM)