A new device for investigating the hydro-mechanical properties of rock joints

A new experimental system composed of two devices is presented for studying the hydraulic conductivity of rock joints and other interfaces in relation with their mechanical loading. This system allows for investigations on the anisotropy of the hydraulic conductivity, as well as for its heterogeneity. The first device controls the injection of a fluid, regulated in pressure or discharge near the centre of the sample of rock joint, which produces a quasi-radial flow within the joint. The output flow is measured in real time using a sectorized peripheral membrane for acquisition of data about the directionality or anisotropy of the flow. The second device allows for the measurement of the evolution of the morphology and of the void map of the rock joints during their mechanical loading (compression or shearing). It is a laser beam moved by an (x, y) frame. This frame is installed within the shear box at several stages of the loading, after temporarily moving one rock wall away from the other one, but without unmounting them from the shear box. After the presentation of the experimental system, and of its performances, we give some examples of test results of replicas of rock joints, loaded in compression and shearing. First, these results show that the change in global transmissivity of the samples is strongly correlated with the normal relative displacement of the rock walls. Several statistical analyses of the change in the void map, taking into account the damage of the asperities of the joint, are presented and compared with the results of the directional output flows. Today further studies involving a FEM as well as a finite volume modelling of the flow within the joints, based on the measured void map are in progress for a more precise comparison to the experimental results. Copyright (C) 2003 John Wiley Sons, Ltd.