Effects of microwave heating on mechanical properties and energy evolution mechanism of granite under conventional triaxial compression

Abstract

To explore the influences of microwave irradiation on the mechanical response mechanism of rock under different confining pressures, granite specimens were subjected to different microwave heating paths, then conventional triaxial compression experiments were conducted. The experimental results show that: 1) As microwave irradiation power and time increase, the density and P-wave velocity of the specimen show a downward trend and the higher the power, the faster the decline; 2) The sensitivity of specimen strength to confining pressure and microwave (power and time) is ranked thus (in descending order): confining pressure, microwave power, then irradiation time. Under a low confining pressure, the strength value of the specimen exhibits a decreased trend with the increase of irradiation time, but with the increase of confining pressure, the change of the strength of the specimen tended to be consistent; 3) The strain energy evolution of the specimen is similar, it is mainly manifested in energy accumulation before the peak, and energy dissipation and release thereafter. Under the influence of microwave radiation, the evolution of dissipation ratio shows a significant microwave effect, but the microwave effect becomes weaker with the increase of confining pressure. Therefore, when using microwave rock-breaking techniques, combined with necessary pressure-relief technique, microwave irradiation can produce the best rock-breaking effect.