Abstract: The dynamic response of X-section cast-in-situ concrete (XCC) pile-raft composite foundation embedded in sand under sine wave loading simulating a moving train axle load with different frequencies is investigated based on large-scale model tests. This study measured the variation of velocity and dynamic soil pressure with depth, and analyzed the response in velocity, dynamic soil pressure and dynamic stress of XCC pile under different load frequencies. It is shown that the amplitude of velocity response of the raft increases approximately linearly with increasing loading frequency. The dynamic stress and dynamic load magnification factor of subsoil also increases gradually with increasing loading frequency. In addition, the dynamic stress on top of the XCC pile increases with increasing loading frequency. The results provide an insight into high-speed railway pile-raft composite foundation regarding to theoretical analysis and calculation, and the determination of dynamic load magnification factor.

Key words: pile-raft composite foundation, XCC pile, loading frequency, dynamic load, model test