Shaking table tests and numerical simulations of dynamic interaction of soil-pile-nuclear island system

The dynamic response characteristics of soil-pile-nuclear island system are studied through the shaking table tests. The distribution pattern of internal force, deformation mode and failure mechanism of piles are analyzed. The test results show that when the RG160 artificial waves of different amplitudes are input, acceleration amplification occurs in both the soil layer and the pile foundation structure. The peak value of the amplification coefficient of the free field far away from the structure appears on the soil surface, while the peak value of the amplification coefficient of the soil layers between piles appears in the middle part, which indicates that the pile foundation has a certain influence on the acceleration amplification of the soil layers. The peak value of the amplification coefficient along pile appears in the middle part and then decreases near the pile cap indicating that the superstructure has a significant effect on the acceleration amplification distribution along the piles. The shear force of pile body is the maximum at the pile-cap connection and decreases with the increase of depth, while the bending moment is larger at the top and middle upper positions of the piles. The pile-cap joint and the middle part of the piles (about 6 times the diameter of the piles) are the weak point of the piles, and the failure modes are tensile shear failure and bending failure. The failure sequence of the pile groups is that the piles at one side along the vibration direction are damaged first and cause the failure of the middle corner piles, then the middle piles are damaged, and the piles at the other side are destroyed finally. The possible failure mechanism of the pile groups under horizontal seismic loads is that the piles at one side along the vibration direction are more likely to be affected and damaged first by the earthquake because of the weak constraint of the around soils, and then cause the destruction of other piles. The conclusion can provide reference for the seismic design of pile foundation of nuclear island plants.