Effect of fracture deformation on fluid pressure distribution—an indicator of slope instability

Abstract

Results from laboratory and field tests on fractured rock systems have shown that changes in fluid pressure within a fracture can cause changes in the effective normal stress that result in significant normal displacements. These normal displacements change the fluid pressure distributions and hence the shear strength of the fracture system. The nature of the normal displacement (opening or closing of the fracture) can be detected by comparing the ratios of pressures measured at two points within the fracture plane. Other workers have shown in laboratory shear tests on rough fractures that movement along discontinuities, prior to failure, has both a normal and tangential component. Careful measurement of changes in fluid pressures in fractured rock slopes should be able to detect the effects of such normal displacements and thus give an indication of an approaching instability.