The gas permeability of coal seam is one of the important indexes of gas drainage. The variation of the permeability of briquette coal samples with the stress under different confining pressure in the processes of unloading confining pressure and axial pressure and loading to the secondary damage process after broken were studied by using the seepage simulation-adsorption and desorption experimental device. The results showed that the permeability of briquette coal after the peak strength increased than the...