Permeability Changes During Shear Deformation of Fractured Rock

摘要

The effect of shear deformation on the permeability of fractured rock has been investigated in drained triaxial compression experiments on prefractured samples of Coconino sandstone. These experiments show that permeability across a fracture decreases with increasing shear deformation because of localized deformation along the fractures and the evolution of a gouge zone. Petrographic observations show a progressive decrease in grain size and porosity of the gouge zone with increasing shear displacement. With increasing normal stress there is a more rapid reduction in grain size and a higher degree of compaction of the gouge per increment of shear displacement, which results in a faster decline in permeability during sliding. Although not tested in this study, the observed localized microfracture zone immediately adjacent to the sliding surface suggests that a narrow channel of high permeability parallel to the fracture might also develop during shear deformation. (ERA citation 12:028305)