Effect of soil-pile-structure interaction on seismic behaviour of nuclear power station via shaking table tests

Abstract To better understand the characteristics of the seismic response of nuclear power stations with fixed-base and pile-raft foundations, a series of shaking table tests were performed. The shaking table tests included three cases: free-field soil, fixed-base structure without soil, and superstructure with a pile-raft foundation embedded in the soil. One white noise excitation and three earthquake motions with different earthquake intensity were selected as the ground motion to identify the seismic response of the structure, raft, piles, and soils. The effects of earthquake intensity, earthquake frequency, soil-pile-structure interaction, and soil nonlinearity on the system dynamic responses were analysed. The test results show that the natural frequency and the damping ratio of the superstructure for the pile-raft foundation and the fixed-base structure are different, owing to the soil-pile-structure interaction effect. The acceleration amplification ratio of the fixed-base superstructure shows a significantly higher value than that of the superstructure with a pile-raft foundation. The average peak acceleration ratio of the raft for the pile-raft foundation (raft/soil surface) is 1.2. Under the long period wave excitations, the bending moment of the pile is greater than that of short-period wave excitations, and the peak bending moment occurs at the pile head. The vertical and horizontal displacement and residual displacement increases with the earthquake intensity. These observations suggested that the design of nuclear power station with a pile-raft foundation embedded in clay cannot be simplified as a fixed-base structure. Moreover, adopting pile-raft foundation for nuclear power station will extend the choice of finding suitable construction sites for the nuclear power stations, and the test results could provide references for engineers.