Gas Flow Characteristics and Optimization of Gas Drainage Borehole Layout in Protective Coal Seam Mining: A Case Study f
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Original Paper
Gas Flow Characteristics and Optimization of Gas Drainage Borehole Layout in Protective Coal Seam Mining: A Case Study from the Shaqu Coal Mine, Shanxi Province, China Zhiheng Cheng,1,3 Hui Pan,1 Quanle Zou,2,5 Zhenhua Li,4,5 Liang Chen,1,3 Jialin Cao,1 Kun Zhang,1 and Yongguo Cui1 Received 28 July 2020; accepted 31 October 2020
With increasing demands for coal resources, coal has been gradually mined in deep coal seams. Due to high gas content, pressure and in situ stress, deep coal seams show great risks of coal and gas outburst. Protective coal seam mining, as a safe and effective method for gas control, has been widely used in major coal-producing countries in the world. However, at present, the relevant problems, such as gas seepage characteristics and optimization of gas drainage borehole layout in protective coal seam mining have been rarely studied. Firstly, by combining with formulas for measuring and testing permeability of coal and rock mass in different stress regimes and failure modes in the laboratory, this study investigated stress– seepage coupling laws by using built-in language Fish of numerical simulation software FLAC3D. In addition, this research analyzed distribution characteristics of permeability in a protected coal seam in the process of protective coal seam mining. Secondly, the protected coal seam was divided into a zone with initial permeability, a zone with decreasing permeability, and permeability increasing zones 1 and 2 according to the changes of permeability. In these zones, permeability rises the most in the permeability increasing zone 2. Moreover, by taking Shaqu Coal Mine, Shanxi Province, China as an example, layout of gas drainage boreholes in the protected coal seam was optimized based on the above permeability-based zoning. Finally, numerical simulation and field application showed that gas drainage volume and concentration rise significantly after optimizing borehole layout. Therefore, when gas is drained through boreholes crossing coal seams during the protective coal seam mining in other coal mines, optimization of borehole layout in Shaqu Coal Mine has certain reference values. KEY WORDS: Gas flow, Gas drainage, Multi-seam mining, Permeability.
1
School of Safety Engineering, North China Institute of Science and Technology, Beijing 101601, China. 2 State Key Laboratory of Coal Mine Disaster Dynamics and Control, College of Resources and Environment Science, Chongqing University, Chongqing 400044, China. 3 NCIST Zhongan Technology (Beijing) Co., LTD, Beijing 101601, China. 4 School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, Henan, China. 5 To whom correspondence should be addressed; e-mail: [email protected], [email protected]
INTRODUCTION As mining depth in coal mines increases, gas content, gas pressure, and absolute gas emission in deep coal seams increase gradually and dynamic disasters, such as coal and gas outburst, are becoming more dangerous (Zou and Lin 2018; Song et al. 2020; Su et al. 2020; Zhang et a
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