Hydraulic pressure effect on mechanical properties and permeabilities of layered rock mass: an experimental study

The triaxial compression tests under different hydraulic pressures and low confining pressure were carried out to study the hydraulic pressure effect on the mechanical properties and permeabilities of layered rock mass. In general, the results show that the increase of hydraulic pressure reduces the peak strength of layered rock mass and the layer structure changes the mechanical properties of rock mass. With the increase of hydraulic pressure, the peak strength of layered rock mass decreases sharply and then slows down. The peak permeabilities of layered rock mass occurred later than the time when the strength come to the peak. The increase of hydraulic pressure will accelerate the propagation of cracks and significantly enhance the peak permeability of layered rock mass. With the increase of the layer number, the effect of hydraulic pressure becomes more distinct. The initial permeability and the peak permeability increase largely. The increase of hydraulic pressure promotes the expansion and penetration of cracks, so the rock mass develops from tensile failure to the composite failure forms including shear failure and interfacial shear slip failure.