Earthquake response of concrete gravity dams including dam–foundation interface nonlinearities

Various possibilities of natural isolation occurring along the dam–foundation interface during an earthquake are studied in order to evaluate the seismic response of an existing gravity dam. A plasticity -based formulation is used in the local stress space of interface elements to model sliding as well as partial opening along the dam base. The resistance to sliding is governed by two Mohr–Coulomb envelope surfaces representing the peak and residual strength of the joints. Effects of base deformation, sliding parameters and foundation flexibility are also investigated. Apart from sliding, other modes of failure of the dam are also identified. The results show that sliding generally reduces the maximum amount of tensile principal stresses in the dam body; however, the amount of reduction is generally not large enough to prevent cracking, especially at the upper parts of the dam.