Roughness control on hydraulic conductivity in fractured rocks

The influence of joint roughness on the typologies of fluid flow inside fractures is well known and, thanks to experiences in the field of hydraulics, it has been studied from both a physical and mathematical point of view. Nevertheless, the formulations adopted by traditional hydraulic models are hardly applicable in the geological field, because of the difficulty encountered in the roughness parameter estimation. Normally this parameter can be estimated using the joint roughness coefficient (JRC), which considers both the asperity height and its regularity and directional trend. The main advantage in using the JRC arises from the fact that it can easily be obtained from geological-technical surveys and from comparison with the standard Barton profiles. Some relationships have been built up that allow for the estimation of the hydraulic conductivity tensor (an essential parameter for understanding water flow in fractured rock masses), not only as a function of traditional parameters like aperture, spacing, dip and dip direction, etc., but also of joint roughness, precisely expressed in terms of the roughness coefficient. These relationships have been studied initially from a theoretical point of view and then practically, through laboratory investigations.