Effect of Water on Granite Deterioration Under Microwave Radiation Based on Real-Time AE Monitoring

Microwave-assisted rock-breaking is highly promising in the process of hard rock tunnel excavation due to its safety and high efficiency. Water plays a pivotal role in the microwave heating process, significantly impacting the effectiveness of microwave-assisted rock fragmentation. Nevertheless, there is a lack of comprehensive research on the influence of water in the process of microwave heating of rocks. This study investigated the influence of water on the response characteristics of granite under microwave irradiation by analyzing the changes in the real-time acoustic emission (AE) signals, porosity, wave velocity, and uniaxial compressive strength of samples with different levels of water saturation. The experimental results revealed the real-time AE characteristics of rock samples were categorized into three periods: a quiet period, a violent period, and an attenuation period. The maximum temperature in the quiet period was about 150 degree celsius, resulting in the proliferation of mineral crystal defects under the action of water, and the intensity of AE counts was positively correlated with water saturation. Simultaneously, the degree of thermal damage to porosity, wave velocity, and uniaxial compressive strength also increased with increasing water saturation. During the violent and attenuation periods, the activity of AE signals increased, yet remained largely unaffected by the the water saturation level. Moreover, the presence of water facilitated the transition of rock samples from elastic to ductile behavior under microwave irradiation. This investigation holds significant importance for the practical application and advancement of water utilization in microwave-assisted rock fragmentation technology. Real-time monitoring of acoustic emission during microwave heating was realized.Acoustic emission characteristics of granite with different saturations were similar.Acoustic emission characteristics before 150 degree celsius were closely related to saturation.