Experimental Study on the Microwave Monitoring of Rock Stress and Fracture

Recent years many authors reported thermal anomaly change around epicenter before earthquake. Some researchers tried to predict the earthquake based on the analysis on the temperature anomaly feature by using satellite thermal infrared data. However the infrared radiation can not pass through the thick-layer cloud, so as to hardly achieve the earthquake monitoring. Microwave is also a kind of thermal radiation and some scholars have found microwave radiation anomaly appearing before earthquake. To explore the feature of microwave emission anomaly before earthquake, a group of physical simulation experiments were carried out. In the experiment, a hydraulic loader (YGA-3000), whose maximum vertical load is 3000 kN, was applied as loading machine for the granite samples. A microwave radiometer was used for microwave emission detection in the loading process of rock. Its detection wavelength is 8 mm, temperature sensibility 0.01◦C. The experimental results showed that microwave emission energy changed along with the change of stress. The microwave emission energy varied little in the beginning loading stage, increased in the elastic loading stage, decreased in the plastic loading stage and increased again in the fracturing stage. The AIRT has the close relationship with the load, but the brightness temperature of microwave emission has the close relationship with the AE energy. The microwave emission precursor for rock failure is more obvious than the AIRT precursor. These experiment results indicated that it was possible to use the microwave remote sensing for monitoring the stress variation and fracturing of rock masses, including earthquakes.