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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 8 | Copyright
Nat. Hazards Earth Syst. Sci., 14, 2125-2132, 2014
https://doi.org/10.5194/nhess-14-2125-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 21 Aug 2014

Research article | 21 Aug 2014

An explanation of large-scale coal and gas outbursts in underground coal mines: the effect of low-permeability zones on abnormally abundant gas

F. H. An1,2 and Y. P. Cheng2,3 F. H. An and Y. P. Cheng
  • 1College of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China
  • 2National Engineering Research Center for Coal & Gas Control, Faculty of Safety Engineering, China University of Mining & Technology, Xuzhou 221116, China
  • 3State Key Laboratory of Coal Resources and Mine Safety, China University of Mining and Technology, Xuzhou 221116, China

Abstract. Large-scale coal and gas outbursts pose a risk of fatal disasters in underground mines. Large-scale outbursts (outburst of coal and rock greater than 500 t) in recent years in China indicate that there is abundant gas in areas of outbursts containing large amounts of potential energy. The adequate sealing properties of the roof and floor of a coal seam are required for local abundant gas around the site of an outburst, but an annular low-permeability zone in a coal seam, which prevents the loss by gas migration through the coal seam itself, is also required. The distribution of coal gas with this annular zone of low permeability is described, and it is proposed that the annular zone of low permeability creates conditions for confining the coal gas. The effect of this low-permeability zone on the gas distribution is analyzed after allowing for simplifications in the model. The results show that the permeability and length of the low-permeability zone have a great impact on the gas distribution, and the permeability is required to be several orders of magnitude less than that of normal coal and enough length is also in demand. A steep gradient of gas pressure in the low-permeability zone and the high-pressure gas in the abundant zone of gas can promote coal mass failure and coal wall deformation, thereby accelerating the coal and gas outburst. The high-pressure gas in abundant zone of gas will lead to a large-scale outburst if an outburst occurs.

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