Seismic analysis of soil-structure system of nuclear power plant on non-rock site via shaking table test

Abstract

The influence analysis of the site condition is a key issue considered in the seismic design of nuclear power engineering on non-rock sites. To study the soil–structure interaction (SSI) effect of the site conditions on the structural seismic response of nuclear power engineering, we used a CAP1400 nuclear power plant as a case study subject and performed a shake table testing of a soil–structure system model. The test results indicate that there are strong nonlinear effects of non-rock site, that is, with increase of seismic input level (peak ground acceleration, PGA), the natural vibration frequency of the soil-structure system decreased significantly, and the damping ratio increased; Under all seismic input levels, the site amplification phenomena occurred in different directions, and the response accelerations of soil and structure in the high-frequency range (>3 Hz) are greatly influenced by the SSI effect; The cracks began to appear in the model soil under lower seismic input level (PGA 0.20 g) and developed, lengthen and widen under the high seismic input level (PGA≥0.30 g), and the soil cracks were almost all connected under the SME seismic input level (PGA 0.51 g), but still no micro-cracks were detected on the model structure; Under the SSE seismic input level (PGA 0.30 g) the contact surface separation appeared on the contact surfaces of the model soil and the structure foundation, and then under the ultra SME seismic input level (PGA 0.84 g) the structure foundation became unbalanced so that the soil-structure system failed. The influence of the site conditions on the seismic response of the structure was significant. The seismic response analysis and seismic design of the nuclear island structure on no-rock sites should take into account the effects of site conditions and soil-structure interaction.