Experimental Study on Mechanics and Permeability Properties of Water-Bearing Raw Coal Samples Under In-Situ Stress

In this paper, we investigated the mechanical and permeability characteristics of water-bearing raw coal samples under in-situ stress, and came to some conclusions, as follows: the peak strength and peak axial strain of samples gradually decrease with the increase of water content. Under the same stress condition, the higher the water content is, the lower the axial strain and radial strain will be. The peak strength and peak strain of the sample both decrease with the water content as a quadratic function. During the post-peak loading and unloading process, with the increase of the number of cycles of loading and unloading, the radial strain decrement and increment of the raw coal sample gradually decrease after loading and unloading confining pressure. The permeability of samples gradually decreases with the loading confining pressure, and the permeability of the sample gradually increases with the unloading confining pressure. The permeability of coal samples increases volatility with the increase of axial strain, and the fitted sample permeability and effective stress are subject to the ExpDec1 function distribution.