Weak current induced by coal deformation and fracture and its response to mine seismicity in a deep underground coal mine
Dexing Li, Enyuan Wang, Xiaojun Feng, Dongming Wang, Xin Zhang, Yunqiang Ju
Abstract
Weak currents can be stimulated from coal and rock materials under a load. To investigate the response characteristics of weak current to coal failure and mine seismicity , both laboratory experiments and field tests on weak current measurement of stressed coals were conducted. The response characteristics of weak current was analyzed, the quantitative relationship between weak current and mechanical behaviors was studied and the precursors of coal failure and mine seismicity based on weak current response were investigated. The results of laboratory experiments show that the weak current increases linearly with stress and strain in the elastic deformation stage and shows an accelerated increasing trend after entering the elastic deformation stage, reaching its peak value when the final failure occurs. A fracture is accompanied by a suddenly increased current (SIC), of which the intensity is proportional to the stress drop. The accelerated increase of weak current accompanied by fluctuations can be used as a precursor of coal failure. The weak current measured in an underground coal mine responds well to mine seismicity that occurs in the increasing process of a SIC. The continuously accelerated increase of weak current can be used as a precursor of mine seismicity, to which the weak current could respond few minutes in advance. It is feasible to use the weak current technique for rockburst prediction in mines and tunnels because of its strong anti-interference ability and early response to mine seismicity and coal/rock failure.