Abstract: Fault fracture zone is an important channel for mine water inrush. Most of the fracture zone is composed of soil-rock mixture(SRM) whose seepage characteristics have an important influence on the prediction and prevention of mine water inrush. To investigate the impact of rock content on the seepage characteristics of SRM in fault fracture zone,SRM samples were remolded in lab from the field-collected mixture of fault gouge and rubble. The permeability characteristics of samples with different rock block proportions were examined under different confining pressures and axial pressures by using GDS tri-axial test system,and the sensitivity of permeability coefficient to rock content change was analyzed. Moreover,the seepage characteristics,the crack propagation and failure of SRM samples with different rock-bearing rates were investigated by using RFPA. Results demonstrated that 1)higher rock content resulted in larger initial permeability coefficient and higher strength of SRM;2)the permeability coefficient reduced with the increase of confining pressure,and the relation between permeability coefficient and axial pressure can be described by exponential function;3)rock content of 40% and 60% had a largest influence on permeability coefficient;4)cracks during the seepage failure of SRM mainly propagated in the soil between the rocks;5)the sudden change point of permeability coefficient was consistent with the peak strength failure point of the sample and the highest point of acoustic emission frequency. The research results offer reference for preventing and controlling geological disasters such as engineering water inrush in fault areas with varied rock content.

Key words: soil-rock mixture(SRM), permeability coefficient, rock block proportion, fault fracture zone, RFPA