Influence of moisture on seepage characteristics of coal during total stress-strain process

In order to study the influence of moisture on seepage characteristics of coal during the complete stress-strain process, the complete stress-strain process with seepage experiment of dry coal sample and full-water coal sample were carried out, and the complete stress-strain characteristics and permeability evolution laws of two coal samples were analyzed. The experimental results showed that the complete stress-strain curve of dry coal sample had five stages, while the full-water coal sample had only four stages. After the peak stress destruction, the axial stress of full-water coal sample fell by 36.82%, and the strain softening phase disappeared in the full stress-strain curve. Compared with dry coal samples, the compressive strength, elastic modulus and peak stress of saturated coal samples decreased by 8.95%, 8.54%, 8.90% and 10.87% respectively. The permeability of dry coal sample increases with the increase of axial strain, and the relationship is linear. The relationship between permeability and strain of saturated coal sample has obvious stages, which can be divided into stable seepage stage and rapid seepage stage. The existence of water will inhibit the gas seepage process of coal body, so the drainage of coal seam should be paid attention to in the gas extraction project.