Abstract: For the purpose of studying the influences of permeability properties affected by the different pore-water pressures, MTS electro-hydraulic servo system has been utilized to conduct the permeability characteristics experiments of specimens from deep coal mine under the conditions of the different pore-water pressures, especially the high pore-water pressures. The results show that the permeability rate curves are quite consistent with volumetric strain curves, which are both U-shaped. Meanwhile, under a certain external condition, the effect of the pore-water pressures on the permeability properties and volumetric-strain depends on the critical threshold pore-water pressures of coal specimens. The permeability properties under higher pore-water pressure than the critical threshold have been improved several times than that under lower pore-water pressure. Moreover, the pore-water pressure has an important influence on ultimate strength of coal rock. The higher the pore-water pressure is, the lower the peak strength is. The more distinctive effects of dilatation emerge, the more strain is needed for the appearance of permeability peak. The research result provides the guidance for the employment of high pore-water pressure to improve the permeability and disaster prevention of coal seam water injection.

Key words: coal seam, high pore-water pressure, permeability properties, whole stress-strain, volumetric strain