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Wang L.,Henan Polytechnic University | Wang Z.,Henan Polytechnic University | Xu S.,Guizhou Qianxi Energy Development Company Ltd | Zhou W.,Guizhou Qianxi Energy Development Company Ltd | Wu J.,Henan Polytechnic University
Journal of Natural Gas Science and Engineering

Protective coal layer mining with pressure-relief gas extraction from the protected coal layer is an effective and economical way of controlling coal and gas outbursts in underground mines. According to a field test of the deformation of the protected coal layer in the Qinglong coal mine, during the mining of the protective coal layer, the floor of the protective coal layer can be divided into five areas in the horizontal direction: the original stress area, the stress concentration area, the stress relaxed area, the stress recovery area, and the recompaction area. From coal bed methane (CBM) extraction with pressure relief, the floor strata can also be divided into five areas: the original gas flow area, the gas flow reduction area, the initial pressure relief area with increasing permeability and flow, the full pressure relief area with high permeability and flow, and the pressure recovery area with decreasing permeability and flow. Mining of a protective coal layer will result in the breakage and movement of the overlying strata as well as floor heaves in the floor strata. In these unloaded coal strata, relieving the stress leads to the production of new cracks, which increases the permeability. The coal deformation and gas desorption are remarkable in the protected coal seam. The maximum dilation and dilation rate were 13mm and 4.19‰, respectively. The gas flow and permeability increased significantly. The maximum natural emission flow and permeability reached 0.194m3/min and 19.75m2/MPa2.d respectively, There were 27- and 42-fold increases in permeability, which indicated that the pressure relief in this region was complete and that fractures in the coal body developed. This emission is conducive to CBM migration and extraction. © 2015 Elsevier B.V. Source

Li X.-J.,China University of Mining and Technology | Li X.-J.,Guizhou University | Zhou W.-G.,Guizhou Qianxi Energy Development Company Ltd
Meitan Xuebao/Journal of the China Coal Society

Based on the variable rules of gas concentration before and after blasting at working-face in coal roadway of Qinglong Mine, this paper put forward a method of peak-to-valley ratio of gas as a way to forecast and predict gas and coal outburst on the working-face. Measured data show that even if in the same working roadway, with the difference of sites and measures, the maximum numeric values after blasting are different and they change relatively clear. And, the average minimum numeric values per day before blasting change with sites and measures, but they change little. Though its general adaptability of critical index mark of outburst is worse, but it is easy to realize real-time forecast and predict. Source

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