深厚软土区桥梁桩基偏位分析及处置措施研究

Research on the Offset Analysis and Disposal Measures of Bridge Pile Foundation in Deep Soft Soil Area

针对深厚软土地区地表堆载造成的桥梁桩基病害问题,对某典型城市高架桥桩偏位案例进行研究,结合有限元计算结果与现场检测结果,阐明了深厚软土区桥梁桩基的偏位机制,研究表明:不平衡堆载导致软土中超孔隙水压力增大,超孔隙水压力的消散导致地基土产生不均匀沉降,使得地基土内部产生水平荷载,同时桩身产生负摩阻力,这是导致桩基产生水平偏位且承载力降低的主要原因;不对称堆载,排水边界的变化,是加剧软土固结效应的潜在因素;当桩基已经产生偏位时,地表卸载对桩身变形的修正作用显著;基于PST的桩基完整性检测结果与桥墩偏位结果验证了有限元计算的合理性,根据仿真结果可以确定桩身的应力分布特征,为桥梁结构加固方案的制定提供参考。

In response to the problem of bridge pile foundation damage caused by surface loading in deep soft soil areas,a typical case of elevated bridge pile displacement in a certain city was studied.Combining finite element calculation results and on-site inspection results,the displacement mechanism of bridge pile foundation in deep soft soil areas was elucidated.The study shows that uneven loading causes an increase in excess pore water pressure in soft soil,and the dissipation of excess pore water pressure leads to uneven settlement of the foundation soil.The main reason for the horizontal displacement and reduced bearing capacity of the pile foundation is the generation of horizontal loads inside the foundation soil and negative frictional resistance on the pile body;asymmetric loading and changes in drainage boundaries are potential factors that exacerbate the consolidation effect of soft soil;when the pile foundation has already deviated,the correction effect of surface unloading on the deformation of the pile body is significant;the integrity testing results of pile foundation based on PST and the displacement results of bridge piers have verified the rationality of finite element calculation.Based on the simulation results,the stress distribution characteristics of the pile body can be determined,providing reference for the development of bridge structural reinforcement plans.