A model for soil-structure interaction - Application to small modular reactors

Abstract

Canada and other countries are contemplating the construction of small modular reactors (SMR) for the generation of electricity. SMRs would be built at a smaller scale than traditional nuclear reactors with anticipated lower up-front capital costs and enhanced safety features. The SMRs would need to be seismically qualified, and shown to withstand the design basis earthquake without loss of containment. In order to assess the seismic qualification of SMRs, a dynamic coupled elastoplastic-hydraulic model for soil behaviors under seismic loadings is developed. The governing equations of the model are based on conservation of momentum for the porous skeleton, and conservation of water mass. Pore water flow is assumed to follow Darcy’s law while the solid skeleton is assumed to be elasto-plastic, with the adoption of the modified Cam-Clay model to simulate its stress-strain behavior. The model is tested with the simulation of dynamic triaxial tests and a shaking table experiment. The results show that the model can capture (1) the development of permanent deformation in soil, (2) the shear-induced volume change (including both contraction and expansion), (3) the generation and dissipation of excess pore water under the dynamic loading, and (4) the strain hardening and softening behavior of soil under complex stress paths. Finally, the model is used for the scoping analysis of the seismic response of a hypothetical SMRs embedded in sandy soils.