Experimental study on deformation characteristics of water imbibition of coal body containing gas

In order to study the deformation characteristics of water imbibition of coal body containing gas, a self-designed pressure-bearing gas natural water absorption test platform was used to carry out isobaric natural water absorption experiments in coal gas adsorption equilibrium pressures at 0.5, 1.0, 1.5, 2.0 MPa. The test results showed that: in the gas adsorption stage, with the increase of pressure, the horizontal and vertical deformation of the coal body showed a trend of increase, the vertical strain was about twice as the horizontal strain. In the natural water absorption stage, the transverse and longitudinal deformation of coal body is greater than that of pure gas adsorption under the same gas pressure. The ambient pressure of the experimental system increased slightly, and the maximum value of pressure increase was 0.013 MPa, indicating that the water imbibition was accompanied by gas desorption process. At the stage of gas desorption and water drainage, under different gas pressures, the water content of coal were 0.98%, 1.05%, 1.51%, 2.24%. The volume strain was secondarily related to the initial gas pressure, the residual deformation value of coal body strain was large, and it showed the irreversibility and destructiveness of gas-containing coal deformation after water imbibition.