Water changes natural seepage in the surrounding geological environment and weaken rock mass of valley during reservoir impounding, which result in large time-dependent deformation of foundation of dam. A nonlinear creep damage model considering water effect is proposed by taking into account the influence of pore pressure on the spherical stress tensor and yield surface. The elastic-viscoelastic model is consisted of a spring and several cascaded Kelvin models. The model is implemented in the ABAQUS user material subroutine. The accuracy of the model is verified by the triaxial creep test of saturated sandstone and dry sandstone. Then it is applied in the valley contraction analysis during impounding of Xiluodu high arch dam.

The maximum mean stress gradient direction in typical plane strain and axisymmetrical plastic deformation problems was calculated by numerical method to investigate relationships between material flow direction and related local stress field. Good agreement was found between the movement direction in the deforming bodies and the maximum mean stress gradient direction of the related local mean stress field. This agreement was also found in typical 3-D problems by numerical simulation and visualization.