The Influence of the Disc-shaped Sandstone Thickness on Permeability during Bending Deformation

 

Luzhen Wang

State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining & Technology, Xuzhou, Jiangsu 221008, China
Department of Fundamental Sciences Teaching, Yancheng Institute of Technology, Yancheng, Jiangsu 224051, China; e-mail: wangluzhen5@126.com

Zhanqing Chen

State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining & Technology, Xuzhou, Jiangsu 221008, China

Hailing Kong

Department of Fundamental Sciences Teaching, Yancheng Institute of Technology, Yancheng, Jiangsu 224051, China

 

 ABSTRACT

The influence of the water-resisting floor thickness variation on the permeability characters of the bending and heaving floor in coal mining above confined water was experimentally researched by the self-designed testing system, and the process of water inrush was simplified to laboratory. The permeability characteristics of disc-shaped sandstones with different thickness during the whole process of bending deformation were tested. The load-time curves and permeability-time curves of the sandstones with different thickness in the process of bending and seepage were analyzed, and their failure modes were observed. The results show that, (1) the peak load increases with the increasing thickness of the sandstone; it is easier to lose its bearing capacity as the sandstone is thinner. (2) the seepage state of sandstone is related to its variation of bending stress state and crack evolution, and the permeability magnitude of sandstones with different thickness varies from 10-14 m2 to 10-11 m2. (3) seepage burst can be prevented by restricting the further deformation of the sandstone after the peak load. (4) failure modes of sandstones were closely related to their thickness, and the fracture plane occurs at the centre tension plane or the constraint shear plane of the disc-shaped sandstone. The experimental results could provide references for the prevention of floor fracture accompanying water inrush in coal mining above confined water.

Keywords: disc-shaped sandstone; bending deformation; permeability; thickness; confined water.

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