Influence of bedrock depth on the seismic response of a nuclear reactor building foundation considering soil structure interaction

Abstract

Earthquakes events can impact on safety of nuclear power plants. With the increasing number of nuclear power plants, the necessity of seismic safety of nuclear power plants becomes higher than ever before. Nuclear reactor building is an important part of nuclear power plant, so the importance to understand its seismic response is critical.Adopting the direct method, this paper utilized FLAC3D to model the soil-nuclear reactor building three-dimensionally on three different site conditions(medium hard soil, soft rock and hard rock).To capture the separation and sliding between the superstructure and the rock/soil deposit, Interface elements were set between the foundation of the nuclear reactor building and the rock/soil surface. The superstructure was simulated by lumped mass model, and the influence of bedrock depth on the seismic response of nuclear reactor building was investigated considering soil structure interaction. Finally, the acceleration response spectrum, shear force, foundation rocking, foundation differential settlement and lateral displacement of the structural members of the nuclear reactor building were obtained. The results show that the displacement and shear force decreased with the increasein bedrock depth in medium hard soil; In the hard rock site, the trends tended to be opposite; However, under the condition of soft rock site, the response of superstructure is more complex. For the foundation rocking and differential settlement, in the medium hard soil site, the reactions decreased with the increase in bedrock depth; In soft and hard rock sites, there is no obvious trend. The differential settlement of foundation can directly reflect the damage of structure. The results show that the differential settlement of foundation in medium hard soil site exceeded the allowable value, so the influence of differential settlement of foundation on nuclear reactor building can not be ignored, which is important for the safety design of nuclear power plant.

Keywords

• soil structure interaction
• nuclear reactor building
• bedrock depth
• seismic response
• hysteretic damping