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Geomechanics and Engineering
  Volume 28, Number 3, February10 2022 , pages 299-311

Mechanical model for analyzing the water-resisting key stratum to evaluate water inrush from goaf in roof
Kai Ma, Tianhong Yang, Yong Zhao, Xiangang Hou, Yilong Liu, Junxu Hou, Wenxian Zheng and Qiang Ye

    Water-resisting key stratum (WKS) between coal seams is an important barrier that prevents water inrush from goaf in roof under multi-seam mining. The occurrence of water inrush can be evaluated effectively by analyzing the fracture of WKS in multi-seam mining. A "long beam" water inrush mechanical model was established using the multi-seam mining of No. 2+3 and No. 8 coal seams in Xiqu Mine as the research basis. The model comprehensively considers the pressure from goaf, the gravity of overburden rock, the gravity of accumulated water, and the constraint conditions. The stress distribution expression of the WKS was obtained under different mining distances in No. 8 coal seam. The criterion of breakage at any point of the WKS was obtained by introducing linear Mohr strength theory. By using the mechanical model, the fracture of the WKS in Xiqu Mine was examined and its breaking position was calculated. And the risk of water inrush was also evaluated. Moreover, breaking process of the WKS was reproduced with Flac3D numerical software, and was analyzed with on-site microseismic monitoring data. The results showed that when the coal face of No. 8 coal seam in Xiqu Mine advances to about 80 m ~ 100 m, the WKS is stretched and broken at the position of 60 m ~ 70 m away from the open-off cut, increasing the risk of water inrush from goaf in roof. This finding matched the result of microseismic analysis, confirming the reliability of the water inrush mechanical model. This study therefore provides a theoretical basis for the prevention of water inrush from goaf in roof in Xiqu Mine. It also provides a method for evaluating and monitoring water inrush from goaf in roof.
Key Words
    goaf; mechanical model; multi-seam mining; water inrush; water-resisting key stratum
Kai Ma, Tianhong Yang, Yong Zhao, Xiangang Hou, Yilong Liu and Junxu Hou: Center for Rock Instability and Seismicity Research, School of Resources and Civil Engineering,
Northeastern University, Shenyang 110819, China;
Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines,
Northeastern University, Shenyang 110819, China
Wenxian Zheng and Qiang Ye: Xiqv Mine, Shanxi Xishan Coal Power Co., Ltd, Taiyuan 030200, China


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