Seismic failure analysis for a high concrete face rockfill dam subjected to near-fault pulse-like ground motions

In the strong seismic zone of Western China, many high concrete face rockfill dams (CFRDs) have been built or designed, and some of these high dams are located in the near-fault region. A near-fault earthquake has relatively long velocity and displacement pulse periods, and a dynamic directivity effect could result in dam failure. However, there are few seismic analysis of high CFRDs considering pulse-like effect. Therefore, it is necessary to investigate the dynamic response of high CFRDs in the near-fault area. In this study, 16 ground motions are selected including 8 pulse-like motions with rupture forward directivity effects and 8 non-pulse motions. The rockfill materials are described using a generalized plasticity model, while a plastic damage model that considers stiffness degradation and strain softening is used to simulate the face slabs. Furthermore, the interfaces between the face slabs and cushions are modeled using interface elements that follow a generalized plasticity model to describe the relative sliding between slab and rockfill. The numerical analysis results indicate that although the near-fault pulse-like ground motion has a moderate impact on the dam acceleration, it has a remarkable impact on the residual deformation of dam and concrete slab damage, especially for the dam crest. The seismic response of the dam increases with an increasing ratio of the peak ground velocity to the peak ground acceleration (PGV/PGA). In addition, even with the similar Arias intensity, the residual deformation of the dam under pulse-like records is larger than those under non-pulse ones. The pulse-like ground motion often generates a high input energy which will cause large deformation of concrete face slab in a short period of time. Therefore, when a CFRD is constructed in the vicinity of an earthquake, the effects of the pulse-like ground motion should be investigated to comprehensively evaluate the seismic safety of the dam.