Macroscopic and microscopic mechanical behavior and seepage characteristics of coal under hydro-mechanical coupling

Abstract

Understanding the physical, mechanical behavior, and seepage characteristics of coal under hydro-mechanical coupling holds significant importance for ensuring the stability of surrounding rock formations and preventing gas outbursts. Scanning electron microscopy, uniaxial tests, and triaxial tests were conducted to comprehensively analyze the macroscopic and microscopic physical and mechanical characteristics of coal under different soaking times. Moreover, by restoring the stress path and water injection conditions of the protective layer indoors, we explored the coal mining dynamic behavior and the evolution of permeability. The results show that water causes the micro-surface of coal to peel off and cracks to expand and develop. With the increase of soaking time, the uniaxial and triaxial strengths were gradually decreased with nonlinear trend, and decreased by 63.31% and 30.95% after soaking for 240 h, respectively. Under different water injection pressure conditions, coal permeability undergoes three stages during the mining loading process and ultimately increases to higher values. The peak stress of coal, the deviatoric stress and strain at the permeability surge point all decrease with increasing water injection pressure. The results of this research can help improve the understanding of the coal mechanical properties and seepage evolution law under hydro-mechanical coupling.

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