Thermo-hydro-mechanical analysis of rapid sliding process in a new and fast ring shear prototype

A new experimental apparatus -emulating the annular shape of the ring shear- has been designed and developed at the Universitat Politecnica de Catalunya to study fast sliding processes promoted by heat induced friction. This mechanism, which involves pore water pressu regeneration and dissipation in the shear band being heated by the frictional work of the sliding motion, has been an accepted explanation for the high velocity reached in the case of Vajont landslide. Nevertheless, lack of in situ and experimental information has become one of the main drawbacks when trying to explain these coupled processes . The prototype, which incorporates electronic control of torque and speed to emulate force and displacement control conditions, can reach high velocity along the sliding surface (up to 30 km/h and of the order of magnitude of the Vajont case) under relatively high total vertical stresses (up to 3 MPa). The design of this complex prototype and the selection of transducers require the use of simulation-aided techniq ues to help with the interpretation of these coupled thermo-hydro-mechanical processes. The paper presents the coupled formulation, the numerical solution adopted and the simplified geometry used for the equipment, as well as selected results of the pore pressure, temperature and shear strength evolutions along the sliding surface of a synthetic fast sliding test. These results are used to better know the location, range, sensitivity and fast response required for the temperature and pore pressure transducers, which are located close to the sliding surface