Variation in the electrical properties of gabbro after microwave heating

Abstract

Microwave assistance has the potential to reduce the energy input required for mechanical rock breaking. This study systematically investigated the changes in electrical properties (specifically resistivity, capacitance, and impedance) of gabbro after microwave heating during the graded loading process, as well as its internal fracture mechanism. The findings indicate that the variations in resistivity, impedance, and capacitance of gabbro can be divided into three stages during the graded loading process: the compaction stage, elastic-steady cracking stage, and nonlinear crack propagation stage. When the strain level exceeds 70%, the resistivity and impedance start to increase, and the capacitance begins to decrease. The study also identifies a significant positive correlation between microwave power and the rate of temperature increase on the rock surface. A critical power threshold of approximately 2 kW is observed, below which achieving rapid temperature rise becomes challenging, but beyond which the temperature escalates swiftly with the energy input. Once the temperature exceeds 350 °C, rupturing mineral inclusions generate numerous microcracks, causing resistivity and impedance to exponentially increase. Furthermore, microwave heating induces a temperature differential exceeding 200 °C between the internal and external regions of the rock. Under the same radiation energy, high-power short-duration radiation is more likely to generate thermally induced cracks within the rock. The rapid expansion and heating of absorbent minerals, as well as the rupture of inclusions, further intensify the propagation of microcracks, greatly reducing the mechanical properties of the rock. This study will provide theoretical guidance for microwave-assisted mechanical rock excavation.