Characterization of rock fissure hydraulic conductivity using idealized wall roughness profiles

Abstract

Changes in fissure hydraulic conductivity that accompany shear and normal rock joint displacements may have a profound effect on total discharges into engineered rock structures. The aperture changes that result from post-peak shear strength deformations commonly overshadow those corresponding to the pre-peak displacements. The form of the post-peak displacements are tensional and shear-dilational opening of fissures. If the surfaces of the matched fissures are idealized as either a sinusoidal or sawtooth form, the changes in hydraulic conductivity that accompany these displacement modes may be evaluated analytically. Assumptions inherent within this characterization approach relate 0o whether the flow may be considered as non-tortuous or tortuous. The former case allows exact analytical expressions to be developed for the conductivity; the latter requires certain simplifying assumptions to be made. For tortuous flow, the approximate analytical representation of the hydraulic conductivity is compared with a numerical solution and shown to yield satisfactory agreement. These results have important ramifications in accounting for deformation induced changes in hydraulic conductivity within fractured rock masses.