Experiment on Effect of Porosity and Dynamic Loading on Permeability of Tectonic Coal Under Negative Pressure Drainage

In order to study the effect of porosity and dynamic loading on gas permeability of tectonic raw coal specimen under negative pressure drainage, a gas-solid coupling triaxial stress servo seepage experimental device was developed. Experimental results show that the porosity has more significant influence on gas permeability of raw coal; the gas permeability increases with the increasing of porosity; under the constant condition of confining pressure, drainage negative pressure and gas inlet gas pressure, the permeability increases slightly with the increasing of the axial compression; after reaching the peak point, it decreases rapidly with the increasing of axial pressure; the gas permeability increased slowly during the axial pressure unloading process, however, it is difficult to restore to the initial permeability; under the condition of maintaining the same confining pressure, axial pressure and gas pressure, permeability increases with the increasing of negative pressure, this effect has little influence under high stress.