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高承台群桩基础是高速铁路桥梁基础的一种常用形式,受到风、地震等荷载作用影响,常常需要承受较大的横向荷载。采用室内物理模型试验和三维有限元程序ABAQUS对软土地层中单桩、群桩的横向承载特性进行了研究,软土采用修正剑桥黏土本构模型,试验结果与有限元计算结果吻合较好。群桩研究方案包括了桩数的变化以及桩间距的变化。结果表明,群桩基础的基桩平均横向承载力(总承载力/桩数)较单桩基础显著增加,且水平荷载方向桩间距越大,其横向承载力越大;群桩基础基桩受力存在三维空间效应,不同位置基桩受力大小排序为角桩最大,其次为边桩,最小为中间桩,弯矩极值差异可达20%,群桩基础桩周土影响范围距外围基桩边缘净距离约为16D(D为桩径)。桩与桩相互影响效应对群桩水平承载不利,承台约束效应对水平承载有利。探讨了考虑上述两种效应的群桩效应系数计算方法,通过计算验证了该方法在软土地区高承台群桩基础横向承载力计算中的适用性。
High cap group pile foundation is a commonly used form of bridge foundation of high-speed railway. Affected by the load such as wind and earthquake, it often needs to bear larger lateral load. The transverse load-bearing characteristics of single pile and group pile in soft soil are studied by indoor physical model test and three-dimensional finite element program ABAQUS. The modified clay model of Cambridge clay is adopted in soft soil. The experimental results are in good agreement with the finite element analysis. The group pile research program includes the change of pile number and the change of pile spacing. The results show that the average lateral bearing capacity (total load capacity / number of piles) of pile foundation of group pile foundation is significantly higher than that of single pile foundation, and the greater the horizontal bearing capacity is, the larger the horizontal bearing capacity is. There is a three-dimensional effect of force. The order of stress of pile at different positions is the largest angle pile, the next one is side pile, the smallest is middle pile, the difference of bending moment can reach 20% The net margin of pile edge is about 16D (D is pile diameter). The interaction between pile and pile is unfavorable to the horizontal bearing of pile group, and the constraint effect of pile cap is beneficial to horizontal bearing. The calculation method of pile group effect coefficient which considers the above two effects is discussed, and the applicability of this method in the calculation of lateral bearing capacity of pile cap pile foundation in soft soil area is verified.