The variation of micro-current in rock under loads and its microcosmic influence mechanism

Abstract

Electromagnetic signal is a key means to monitor rock dynamic disasters. Its essential reason is the free movement of charges. At present, the variation law of microcurrents and the influence mechanism are still not clear in the loading process of rocks with different lithologies. Therefore, an electrical and mechanics experimental system of rock was established to explore the change rules of microcurrents generated in the loading process of rocks and the microscopic influence mechanisms. The research results showed that the microcurrent curves of different rocks had different change laws under low and high loading rates. At a low loading rate, the microcurrent was small and then increased exponentially. While the microcurrents went through three stages at high loading rates: rapid growth phase, gentle phase and mutation phase. The overall microcurrent level of marble was lower than granite and sandstone due to the lack of quartz. Quartz in the rock played a key role in current generation rate of loaded rock, but it was not a decisive factor. With a higher quartz content, the average current generation rate increased with the increase of grain size of the quartz crystal. Under the uniaxial compression of the rock, the piezoelectric effect and fracture power generation currents played the major role at different stages, and the piezoelectric-fracture synergy power generation mechanism was put forward. The research results could provide a theoretical basis for the mechanical influence mechanism of current generation during rock fracture process.