Real-time evolution and connectivity of mined crack network

Abstract：Based on the field conditions of coal mining face No. 15-14120 at No. 8 Mine of Pingdingshan Coal Mining Group, the information for real-time evolution of coal-rock crack network with advancement of working face was collect- ed by using improved intrinsically safe borehole video instrument. Fractal theory and projective arithmetic for the two- dimensional connectivity of cracked rock mass were employed to characterize the evolution of crack network and varia- tion of connectivity caused by mining. The results show that the influenced domain of crack network ahead of the work- ing face is 50 m approximately in the condition of coal mining face No. 15-14120 at No. 8 Mine of Pingdingshan Coal Mining Group, and the calculated fractal dimension of crack network increases as the distance between the monitoring hole and the mining face decreases,which exhibites a good agreement with the variation of pressure at overburden stra- ta. Moreover, the calculated connectivity of mining-induced crack network increases obviously with the advancing of mining-face and the increasing process can be divided into linear phase, exponential phase and constant phase.