Strength Degradation and Fracture Mechanism of Sandstone under Microwave Irradiation

To study the strength deterioration and fracture mechanism of rock under the microwave irradiation, the experiments on the wave velocity and Brazilian splitting tensile strength of sandstones after different microwave irradiation time were carried out. The microstructural evolution of sandstone were studied by means of thermogravimetric (TG) analysis and electron microscope scanning (SEM). The results show that the surface temperature of sandstone increases rapidly under microwave irradiation. The P-wave velocity and tensile strength decreased continuously with the increase of irradiation time under 3 kW power. Considerable macroscopic cracks appeared on the surface of the sandstone after microwave irradiation for 6 min. The high temperature generated by microwave irradiation leads to physical and chemical changes of rock minerals, and the selective heating of microwave results in thermal stress. All these have caused damage to the rock, and led to the deterioration of macro physical and mechanical properties of sandstone.