A New Approach for In Situ Characterization of Rock Slope Discontinuities: The "High-Pulse Poroelasticity Protocol" (HPPP)

The High-Pulse Poroelasticity Protocol is an alternative approach for in situ rock-slope- properties estimation. It relies on an innovative probe that allows simultaneous pressure and deformation measurements in boreholes. The method consists of short-duration hydromechanical pulse tests to estimate local hydraulic and mechanical properties of fractures (normal, shear stiffnesses and permeability). Then, a long-term injection induces a large slope deformation, measured at the injection point with the HPPP probe and in the near field with tiltmeters. Fully coupled, hydromechanical, numerical elastic models are then used to match all pressure, deformation, and tilt measurements by adjusting discontinuity properties. Applied to a rock slope of fractured limestone, the Coaraze slope in southern France, the method evidenced a hyperbolic relationship between hydraulic apertures and stiffness of fractures, and enabled an estimation of fracture compressive and shear strengths. Compared to other approaches based on joint roughness analyses, this approach seems less subjective and more accurate.