Abstract
To analyze the internal pore evolution law of aquifer rock in a coal mining front under the coupling effect of stress and seepage and the influence on the water inrush performance of the working face, research on the working face was conducted to improve the RTR-1000 high-temperature and high-pressure rock triaxial mechanical testing system, using hollow cylindrical and complete sandstone samples and by considering the stress change law in the actual mining process as the reference loading path. At the initial stage of loading, the permeability of sandstone demonstrates a rapid downward trend within a small range of stress change, with a decline rate of 50%. At lower permeabilities, the fluctuation is small; the plastic and failure stages are transient, and the relationship curve between the horizontal permeability and the axial confining pressure of sandstone is divided into compaction, multiple fluctuations, surrender, and failure. In several stages, the sandstone lateral permeability experiment under the coupling effect of stress and seepage demonstrates that the permeability of the aquifer in the coal mining front is significantly reduced after the original rock stress is disturbed by mining, suggesting that the water inrush calculation of the traditional water-flowing fractured zone and caving zone aquifer rock permeability experiment is inaccurate. Further research can deepen the stress and seepage coupling evolution process under the action of working face water inrush.
Highlights
Underwater coal mining inevitably involves problems such as water gushing on the working face, water inrush into the tunnel, and groundwater seepage. e interaction between the coal strata and groundwater influences the coal seam and groundwater, and there exists a coupling problem between seepage and stress. e coupling of seepage and stress is manifested mainly when seepage occurs; the water pressure caused by seepage acts on the rock and changes its condition
Reichenberger et al proposed a finite volume method for vertex centers that can be used for the complete coupling of two-phase flow in porous media fractures [12]
Gui et al reported that the primary cause of karst water inrush was the coupling effect of mining stress and bottom seepage [18]
Summary
Underwater coal mining inevitably involves problems such as water gushing on the working face, water inrush into the tunnel, and groundwater seepage. e interaction between the coal strata and groundwater influences the coal seam and groundwater, and there exists a coupling problem between seepage and stress. e coupling of seepage and stress is manifested mainly when seepage occurs; the water pressure caused by seepage acts on the rock and changes its condition. Zhao et al proposed a stress and seepage coupling research method based on digital image technology under the same conditions [16]. Wang and Zhang proposed a numerical simulation method for fracture propagation and closure under seepage stress coupling that was modeled using the extended finite element method based on the research background of fractures and voids [17]. Shan and Lai, Sheikh and Pak, Guo et al, and Zhang et al conducted related research on stressing osmotic coupling using numerical simulation, establishing numerical models of rock stress-strain-permeability coupling, and preliminary studies on the mechanism of stress-seepage coupling [25,26,27,28]. E aforementioned research has laid the theoretical foundation for investigation in this study of the coupling of underground stress and permeability under the condition of damage caused by coal mining. The vertical in situ stress is applied under axial pressure, and the horizontal in situ stress is applied under confining pressure, which better simulates the actual stress. e conventional permeability measurement can only measure the axial permeability; the permeability measurement method must be improved to obtain the lateral permeability measurement of the conventional pseudotriaxial apparatus
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