SEISMIC PERFORMANCE EVALUATION OF EPS COMPOSITE SOIL FOUNDATION-CAISSON USING SHAKING TABLE MODEL TESTS

A series of shaking table tests are conducted to study the seismic performance of caisson structure under saturated sand foundation (CSS) and EPS composite soil foundation (CES). The dynamic response characteristics of soil and the dynamic stability of caisson structure are analyzed. The force state and instability mechanism of caisson under dynamic loading are discussed. The influence of CES on seismic stability of the upper caisson structure is discussed. The experimental results indicate that the development rate of excess pore pressure under CES conditions is significantly lower than that under CSS, and EPS composite soil can significantly improve the liquefaction resistance. The dynamic earth pressure acting on the caisson is triangular along the depth direction, and it is the largest at the middle of the caisson. The dynamic response of the caisson under CES conditions, including acceleration, displacement and rotation angle, is smaller than that under CSS conditions, which shows better seismic performance. There is an obvious phase difference between the dynamic earth thrust and inertia force of CES caisson, which is conducive to improving the stability of caisson structure.