Experimental study on permeability characteristics for containing-gas raw coal under different stress conditions

The experimental study on permeability characteristics for raw coal under different stress state is implemented by applying the triaxial self-made \"THM coupled with servo-controlled seepage apparatus for containing-gas coal\", the result indicates: The flow rate of coal sample gradually decreases with the nonlinear loading of axial pressure and increases with the nonlinear unloading of axial stress and confining pressure. The flow rate, axial stress and confining pressure curves all satisfy the negative exponential function relation. When the sample reaches the peak intensity, the sample will be destroyed and the stress will drop rapidly, then the flow rate of the sample will increase rapidly. At this stage, the flow rate and axial strain show an oblique \"v\" pattern. The flow rate of coal sample increases nonlinear with the increase of gas pressure, the relation curve between flow rate and gas pressure satisfies power function relation. Under the condition of same confining pressure and ...