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Geomechanics and Engineering
  Volume 24, Number 5, March10 2021 , pages 479-490
DOI: https://doi.org/10.12989/gae.2021.24.5.479
 


Effects of the borehole drainage for roof aquifer on local stress in underground mining
Jianli Shao, Qi Zhang, Wenquan Zhang, Zaiyong Wang and Xintao Wu

 
Abstract
    Pre-drainage of groundwater in the roof aquifer by boreholes is the main method for prevention of roof water disaster, and the drop in the water level during the drainage leads to the variation of the local stress in the overlying strata. Based on a multitude of boreholes for groundwater drainage from aquifer above the 1303 mining face of Longyun Coal Mine, theoretical analysis and numerical simulation are used to investigate the local stress variation in the process of borehole drainage. The results show that due to the drop in the water level of the roof aquifer during the drainage, the stress around the borehole gradually evolved. From the center of the borehole to the outside, a stress-relaxed zone, a stress-elevated zone, and a stress-recovered zone are sequentially formed. Along with the expansion of drainage influence, the stress peak in the stress-elevated zone also moves to the outside. When the radius of influence develops to the maximum, the stress peak position no longer moves outward. When the coal mining face advances to the drainage influence range, the abutment pressure in front of the mining face is superimposed with the high local stress around the borehole, which increases the risk of stress concentration. The present study provides a reference for the stress concentration caused by borehole drainage, which can be potentially utilized in the optimal arrangement of drainage boreholes in underground mining.
 
Key Words
    mine water disaster; drainage; borehole; radius of influence; stress concentration
 
Address
Jianli Shao, Wenquan Zhang, Zaiyong Wang and Xintao Wu: State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology, Shandong University of Science and Technology, Qingdao 266590, China

Qi Zhang: Department of Civil and Environmental Engineering, Stanford University, Stanford CA 94305, U.S.A.
 

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