Study of Cerchar abrasive parameters of granite under varying microwave penetration depths and its application for evaluating cutting efficiency

To clarify the depth-dependent effects of microwave penetration on thermal damage, strength degradation, and cutter-wear potential in granite, single-sided microwave irradiation tests were performed on stacked granite-slab specimens at a constant power of 2 kW for exposure durations of 5–30 min. The temperature, P-wave velocity, uniaxial compressive strength (UCS), elastic modulus and Cerchar Abrasivity Index (CAI) response were measured at different depths, and empirical CAI-based models were used to predict variations in cutter wear and service life. The results indicate that microwave-induced damage exhibits a pronounced spatial gradient along the penetration direction. The peak temperature and primary damage zone were concentrated at a depth of approximately 6–8 cm, corresponding to the third and fourth layers, while the overall thermal influence extended to about 20 cm. Damage intensity gradually diminishes with depth. The 15–20 min interval is identified as the critical stage of rapid damage evolution, marked by the simultaneous deterioration of P-wave velocity, UCS, elastic modulus, and CAI. The Cerchar results further demonstrate that microwave treatment effectively reduces the cumulative abrasive capacity of granite against the steel pin and the cutter. Considering rock weakening, cutter-wear reduction, treatment duration, and energy consumption, the 20-min irradiation condition provides a favorable engineering balance for the tested Zhangzhou granite under the present 2 kW single-sided microwave irradiation condition.