强震作用下液化场地群桩动力响应及p-y曲线

为研究液化场地中群桩在强震作用下的动力响应特征及桩侧土抗力-桩土相对位移（p-y）曲线规律，依托海文大桥实体工程，基于振动台模型试验，开展了0.15g～0.35g地震动作用饱和粉细砂土层不同埋置深度下的砂土孔压比、桩身弯矩及p-y曲线动力响应研究。结果表明：地震动强度达到0.25g时，不同埋置深度下的饱和粉细砂土层孔压比均大于0.8，产生液化现象，且随埋置深度增加，孔压比增长时刻明显滞后；不同埋置深度下，桩身弯矩最大值均位于液化土层和非液化土层分界面处；同一埋置深度时，随地震动强度的增大，p-y曲线所包围的面积逐渐增大，其整体斜率逐渐变小，说明桩-土相互作用动力耗能逐渐增大，桩周土体刚度逐渐减小；随埋置深度增加，p-y曲线所包围的面积逐渐减小，其整体斜率逐渐增大，说明桩-土相互作用动力耗能逐渐减小，桩周土体刚度逐渐增大。因此，液化场地桥梁群桩抗震设计时，应综合考虑液化土层与桩基础的相互位置关系，确保桩基础在液化土层与非液化土层分界处的抗弯承载能力。

Dynamic response and p-y curve of pile groups in liquefaction site under strong earthquake

To investigate the dynamic response characteristics of pile groups in liquefaction sites under strong earthquakes as well as the laws between soil resistance and pile-soil relative displacement (p-y), a shaking table model test associated with the project of Haiwen Bridge was conducted. The dynamic responses of sand pore pressure ratio, pile bending moment and p-y curve under different embedded depths of saturated silty sand encountered by 0.15g-0.35g seismic action were studied. The results show that when the seismic intensity reaches 0.25g, the pore pressure ratio of saturated silty sand under different embedded depths is larger than 0.8 and the liquefaction phenomenon occurs. As the embedded depth increases, the increased time of the pore pressure ratio is obviously delayed. At different embedded depths, the maximum bending moment of the pile appears at the interface between liquefied soil layer and the non-liquefied soil layer. At the same embedded depth, the area surrounded by the p-y curve increases gradually with seismic intensity, and its overall slope decreases, indicating that the dynamic energy dissipation of pile-soil interaction increases gradually and that the stiffness of soil around the pile decreases gradually. As the embedded depth increases, the area enclosed by the p-y curve gradually decreases and its overall slope gradually increases, indicating that the dynamic energy dissipation of pile-soil interaction gradually decreases and the soil stiffness around the pile gradually increases. Therefore, when performing the seismic design of bridge pile groups at liquefied sites, the relationship between liquefied soil layer and pile foundation should be considered comprehensively to ensure the bending bearing capacity of the pile foundations at the boundary between liquefied and non-liquefied soil layers.