Analysis of the in situ Hydromechanical Behavior of a Fractured Calcareous Rock Mass

Summary. Hydromechanical experiments have been carried out since 1997 within a small fractured calcareous rock mass in southeastern France, at a site called Coaraze. Simultaneous measurements of fluid pressure and joint displacement were performed during these experiments. The interpretation generated has led to characterizing various types of hydromechanical behavior of the jointed rock mass and has provided several lessons. An original analytical interpretation, coupled with a modeling approach, has allowed one to derive the in situ normal joint stiffness, which proves to be highly non-linear. It has been shown that a coefficient able to take into account stiffness contribution from the surrounding rock mass must be included in order to fully interpret the pressure-displacement curves. This analytical interpretation also yields an estimate of the normal stress across the fracture. A comparison between in situ data and laboratory tests is also presented.