Rock progressive failure is usually accompanied by development of cracks. The propagation behaviour of rock cracks is closely related to the evolution of rock permeability. In order to investigate the permeability properties of rock during progressive failure

a series of hydro-mechanical triaxial coupling tests is carried out on tuff specimens under different confining pressures and seepage pressures using triaxial servo-controlled seepage equipment. Based on the experimental results

the following conclusions are drawn. At the stable crack growth stage

the permeability keeps low and stable and the permeability corresponding to crack initiation strength can be used to determine the minimum value of permeability. At the crack unsteady growth stage

the permeability increases significantly and the increase of permeability can be divided into two stages

which can be reflected by crack circumferential strain. The inflection point of crack circumferential strain curve is used to identify the initial permeability. At the softening stage after failure

the permeability decreases and enters into a residual stable stage

which can be reflected by crack circumferential strain rate. The circumferential strain rate can be used to determine the position of the peak of permeability.