Study on permeability evolution law of overburden under repeated mining in weakly cemented strata

Abstract

In order to study the permeability evolution law of coal measure strata during multi-seam mining of weakly consolidated strata in western China, based on the double coal seam mining of Yixin Coal Industry in Ili Mining Area, Xinjiang, a numerical calculation model of weakly cemented strata is established, and the permeability evolution law of weakly cemented coal measure strata, the stress distribution characteristics of overburden and the development characteristics of plastic failure under the condition of repeated mining are analyzed. The results show that: the stress concentration coefficient of the peak value of abutment pressure reaches 1.81 during the process of mining near upper coal seam, and the maximum tensile stress of overburden in goaf reaches 0.9 MPa; the upward and downward cracks in the goaf conduct when the advance distance of the working face reaches 300 m; after coal mining, the pore pressure of overburden decreases significantly, and the mining-induced overburden seepage field presents a distribution law of large seepage velocity around the goaf and small seepage velocity in the middle, and the seepage velocity of coal wall side of working face is greater than the seepage vector of cut hole side, the simulation shows that the seepage velocity increases greatly when the ascending and descending fractures are conduction; when the failure zone between coal seams is first penetrated through, the fan-shaped seepage field is formed between the upper and lower coal seams with high seepage velocity in the middle and low seepage velocity on both sides, and with the continuous advance of the working face, the maximum seepage velocity lies in the front of the working face.

Keywords

• weak cementation
• mining-induced overburden
• permeability evolution
• numerical simulation
• repeat mining