Experimental study on coal deformation induced by gas adsorption-instantaneous pressure relief under unconstrained stress state with different pore structures

In order to clarify the adsorption-instantaneous pressure-relief deformation characteristics of coal with different pore structures under unconstrained stress state, and to reveal the kinetic characteristics of adsorption and rapid desorption of coal with different pore structures. Through adsorption-instantaneous pressure relief test, the coal adsorption expansion deformation and instantaneous pressure relief induced deformation were quantitatively characterized, and the deformation and failure of coal with different pore structures were observed in the process of gas adsorption-instantaneous pressure relief. The results indicate that by comparing the axial strain and radial strain, the deformation of raw coal has anisotropic characteristics, and the axial strain is always larger than the radial strain. The characteristics of pore structure and specific surface area affect the adsorption characteristics of coal to a certain extent. The larger the pore volume and specific surface area, the greater the adsorption expansion deformation of the coal. and the microporous content plays a controlling role in the rapid desorption process of gas. With the decrease of particle size, the size of the matrix becomes smaller, and the gas diffusion path becomes smaller, which accelerates the desorption and diffusion of gas in the matrix. The research results provide a reference for the study of the microscopic mechanism and outburst mechanism of coal seam gas storage and transportation.