不同激振频率下现浇X形桩桩-筏复合地基模型试验研究

Experimental study of XCC pile-raft composite foundation under different excitation frequencies

基于大比例模型试验,采用能够近似模拟列车单个轮轴荷载的正弦波荷载,在砂土地基中通过开展不同激振频率下X形桩桩-筏复合地基的动力特性模型试验,研究激振频率对X形桩-筏复合地基动力响应的影响。着重分析了不同激振频率引起的X形桩-筏复合地基的速度、动土压力、桩身动应力等,获得了速度响应、桩身动应力随深度的变化规律。结果发现:筏板的速度响应幅值随着激振频率的增加近似呈线性增加;地基表面动土压力和动力荷载放大系数随激振频率的增大而增大,且增幅逐渐加大;桩顶动应力随激振频率的增大而逐渐增大。相关研究成果可为我国高速铁路桩-筏复合地基的理论分析与计算以及动力荷载放大系数的确定提供参考依据。

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.