Abstract: The mixture of fault gouge and rubble which taken out from fault zone is used to make the soil-rock mixture(SRM) sample with rock block proportions of 20%, 30%, 40%, 50%, 60% and 70% respectively, and using GDS triaxial test system to measure the seepage characteristics of SRM sample under the different loading and unloading confining pressures, to research the variation law of permeability coefficient of the SRM(soil-rock mixture) sample with different rock block proportions under different confining pressure levels. The test results show that: (1) The permeability coefficient of the SRM sample with different rock block proportions decreases as the pressure increases; and the decrease rate of permeability coefficient in the initial stage of confining pressure loading is obviously higher than in the semi-late period. (2) In the stage of confining pressure loading and unloading, the permeability coefficient of SRM sample at different confining pressure levels present a common trend that with the increase of rock block proportion; it decrease first then increase, the permeability coefficient of the sample with rock block proportion 40% is the smallest; 70% is the largest. (3) In the stage of confining pressure unloading; the recovery degree of permeability coefficient of SRM sample is ascend with the increase of rock block proportion, and the recovery rate of SRM sample with rock block proportion 70% reached 50.2%. (4) In the stage of confining pressure loading and unloading; the sensitivity of the permeability coefficient of SRM sample to the rock block proportion showed a rule of decrease first, then increase and then decrease; and when rock block proportion reached 60%, the sensitivity is highest. (5) In the stage of confining pressure loading and unloading, the relationship between permeability coefficient and confining pressure can described by exponential function.

Key words: fault zone, rock-bearing rate, soil-rock mixture(SRM), confining pressure loading and unloading, seepage characteristics