An in-situ seepage testing method for fractured zones of rock mass

The permeability characteristics of rock mass discontinuities are important to hydropower station project stability. In this paper, a large-scale in-situ seepage testing method is proposed and used to test gentle-dip bedding faults (C3 zone) and steep faults (F14) in a hydropower station construction field in China. The in-situ test results are compared to those of both undisturbed and reconstituted specimens. The comparison indicates that the largest critical hydraulic gradient and smallest seepage permeability coefficient are obtained via in-situ tests since they are performed under stress states that simulate the natural stress of the surrounding rock mass. The natural stress of the surrounding rock mass cannot be reflected in tests of undisturbed and reconstituted specimens.