Experimental study of hydro-mechanical behaviour of closed fractures in a granite

This paper describes an experimental study of hydro-mechanically coupled behavior of rock fractures. A new equipment for shear and compression testing on closed or open fractures is introduced, with which the coupling effects between gas or water and the rock fractures subjected to different loading can be modelled. Mechanical and hydraulic properties of fractures and the coupled parameters are investigated. A series of tests indicate that the closed fractures of a granite has a linear mechanical behavior before failure. Initial hydraulic permeability is of the same order as the intact granite (10(-20)m(2)). The permeability of the fractures significantly increases when shear strengths is exceeded. Calculated hydraulic aperture to water is about 4 mu m. The permeability to water is five times less than that to gas.