Acoustic emission characteristics of gabbro after microwave heating

In recent years, microwave mechanical rock breaking-an energy-saving technology with environmental benefits and high efficiency-is increasingly being used to improve the rock-breaking efficiency of geothermal well drilling. Herein, we studied the evolution of different types of cracks in gabbro under uniaxial loading using the acoustic emission (AE) technique. The results show that, after microwave heating, the number of microcracks in gabbro increases and AE becomes more and more active. During the loading process, AE characteristics can be divided into three typical periods: the peak period, silent period, and active period, which are closely related to the deformation process of the rock. When the heating power exceeds 3.3 kW, the proportion of shear cracks increases with increases in irradiation energy. With an increase in stress level, the proportion of tensile cracks increases, but near failure, shear fracture is still dominant. Under the same irradiation energy, the combination of high heating power and low heating time is more conducive to rock failure. Further, when the heating power is greater than 3.3 kW, the damage to rock is more obvious. The test results provide a theoretical and experimental basis for determining the optimal microwave irradiation conditions to improve rock-breaking efficiency in geothermal development.