Study on Heating-Damage-Cracking Regularity of Microwave Irradiation of Hard Basalt

Wave velocity and uniaxial compressive tests were performed on basalt specimens before and after microwave radiation. The correlation mechanism between heating, damage, and cracking in microwave-irradiated rocks was investigated by combining scanning electron microscope tests with macro-and microfracture analysis. The results show that: Under 1.4 kW microwave irradiation, the two ends of the specimen heated up rapidly at first, followed by slower heating in the middle, resulting in a bimodal temperature distribution with higher temperatures at the ends and lower temperatures in the center. After microwave heating, the longitudinal wave velocity of the specimen gradually decreased with increasing radiation time. Both the damage factor and strength loss coefficient increased progressively with radiation time. The inflection point for the damage factor in wave velocity occurred between 160 and 180 seconds, and the inflection point for the strength loss coefficient was between 160 and 200 seconds. After the “inflection point”, the damage factor reached a plateau and no longer exhibited significant changes with continued radiation. The inhomogeneous temperature distribution within the specimen—due to the microwave heating—induced microcracks, and crack expansion occurred in three stages: crack initiation (0~160 s), crack expansion stage (160~240 s), and collapse and damage stage (after 300 s). The most significant crack expansion occurred during the steep increase in both the damage factor of wave velocity and the strength loss coefficient. The findings of this study can provide valuable insights and references for microwave radiation effects on hard rocks under similar conditions.