Experimental and Simulation Studies on Microwave Treatment for Enhancing Conical Pick Indentation of Granite

Microwave radiation can be employed to pre-damage hard rock to reduce the cost of cutting and excavation in mining. In this paper, laboratory experiments and electromagnetic thermo-mechanical simulations are conducted to investigate the effects of different microwave treatment times on the indentation efficiency of granite using a conical pick. The results show that microwave heating simplifies the indentation stages, and reduces peak pick force and indentation depth. Similarly, acoustic emission (AE) activity and accumulative AE energy decrease as the exposure time increases. Scanning electron microscopy (SEM) analysis confirms that microwave pretreatment causes thermal microcracking, altering the failure mode, surface roughness, and fracture mechanisms around the indentation pit. Numerical simulations further validate that the inhomogeneous temperature distribution within the rock leads to tensile damage, which weakens the mechanical properties of the granite and reduces compressive damage during pick-cutting. The analysis of microwave heating efficiency, specific cutting energy, cutting work, and acoustic emission energy over various exposure times reveals significant energy efficiency at 120 and 180 s. This study elucidates the mechanisms of microwave-assisted cutting and provides insights into optimizing microwave treatment time to reduce energy costs.