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Fracture evolution and gas transport laws of coal and rock in onekilometer deep coal mine with complicated conditions

ABSTRACT
As coal mining gradually extends deeper, coal seams in China generally show high stress, high gas pressure and low permeability, bringing more difficulty to coal mining. Therefore, in order to strengthen gas extraction, it is necessary to carry out reservoir reconstruction after deep coal seams reached. In this paper, the distribution and evolution laws of fracture zone overlaying strata of J15 seam in Pingdingshan No. 10 coal mine after excavation were studied by combining similar simulation and numerical simulation, meanwhile, the gas transport law within fracture zone was numerically simulated. The results show that the fracture zone reaches a maximum of 350 mm in the vertical direction and is 75 mm away from W9,10 coal seams in vertical distance. Since W9,10 coal seams are in an area greatly affected by the bending zone of J15 coal seam under the influence of mining, the mining of J15 coal seam will exert a strong permeability enhancement effect on W9,10 coal seams. J15 coal seam can act as a long-distance protective layer of W9,10 coal seams to eliminate the outburst danger of the long-distance coal seams in bending zone with coal and gas outburst danger, thereby achieving safe, productive and efficient integrated mining of coal and gas resources. The gas flux of mining-induced fractures in the trapezoidal stage of mining-induced fracture field is far greater than that in the overlaying stratum matrix. The horizontal separation fractures and vertical broken fractures within the mining-induced fracture field act as passages for gas flow. Compared with gas transport in the overlaying stratum matrix, the horizontal separation fractures and vertical broken fractures within the mining-induced fracture field play a role in guiding gas flow. The research results can provide theoretical support for the arrangement of high-level gas extraction boreholes in roof fracture zones.
KEYWORDS
PAPER SUBMITTED: 2018-05-26
PAPER REVISED: 2018-06-21
PAPER ACCEPTED: 2018-11-15
PUBLISHED ONLINE: 2019-04-14
DOI REFERENCE: https://doi.org/10.2298/TSCI180526126Z
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