To control methane emissions in gob into longwall working faces, it is necessary to understand the distributions of methane enrichment zones (MEZ) around mined coal seams with different incidence angles. In this paper, FLAC3D software is used to calculate the three-dimensional stress distributions in MEZ in gobs with coalbed incidence angles ranging from 0° to 50°. The results show that MEZ consistently exhibit a "hexagon" shape, and rotate in a clockwise direction as the coalbed angle increases. The MEZ range above the mined seam is larger than that below the mined seam. As the coalbed angle increases, the MEZ range in the roof decreases, while the MEZ range in the floor increases. The MEZ height increases significantly as the coalbed angle increases. The MEZ widths in coal pillars of gobs increase slightly as the coalbed angle increases. The methane concentration increases exponentially as the height in the MEZ increases. The surface borehole bottoms located relatively higher in the MEZ can drain methane with a higher concentration and flow rate, as verified by a field test in the Pansan mine, China.


Mining Engineering


This research was supported by the National Science Fund for Excellent Young Scholars (No. 51422404), the National Natural Science Foundation of China (51504160, 51574172), the Key Scientific and Technological Coal Projects of Shanxi Province (MQ2014-12), the Coalbed Methane Joint Research Foundation of Shanxi Province (2015012008), the Province the Program for the Innovative Talents of Higher Learning Institutions of Shanxi and the Team Foundation of Taiyuan University of Technology (No. 2014TD001), and the Natural Science Foundation of Shanxi (201701D221233). This work was also supported by Independent Research Projects of State Key Laboratory of Coal Resources and Safe Mining, CUMT (14KF03).

Keywords and Phrases

Coal mine; Longwall gob; Methane drainage; Methane enrichment zone; Stress distribution

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Article - Journal

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Publication Date

01 Sep 2017