饱和地基下桩柱结构地震响应

Seismic response of piles structure in saturated soil foundation

通过建立两相饱和地基下桩-土耦合系统的动力分析有限元数值模型,对饱和自由场地基以及桩柱结构在地震作用下的动力响应进行数值模拟研究。结果表明:在地震作用下超孔隙水压沿深度方向呈现出指数衰减趋势,在地表处更易导致地基液化从而散失承载能力。随着超孔隙水压的上升土体强度降低后,饱和地基土层对地震波的高频成分有明显的选择性滤波作用。在桩柱结构地震响应分析中,受桩土间动力耦合作用的影响,桩侧土体比远场地基土更易液化。随着地基承载力的降低,导致桩柱动力以及弯矩响应上升。研究结果与已有桩基础震害经验相符,其方法和结论可对饱和可液化地基抗震工程提供参考。

Through the developed FEM model of pile-soil coupled system with two-phase saturated soil foundation, the seismic simulation of a saturated free field and a pile structure are carried out in this paper. The results indicate that the distribution of excess pore water pressure shows exponential attenuation pattern from ground surface, the soil near the ground surface more tends to be liquefied and loses beating capacity.Along with the rising of excess pore water pressure and the corresponding degradation of soil strength, the saturated free field shows obvious selective filtering of the high-frequency components in earthquake wave. In the seismic response of pile structure, owing to the coupled pile-soil interaction, the surrounding soil more tends to be liquefied.The decrease of foundation＇s bearing capacity leads to larger seismic response and bending moments of structure piles. The conclusions derived in this paper agree with practical engineering experiences, and the numerical method and conclusions could provide some guidance for seismic design of structures in liquefiable saturated soil foundation.