中文摘要：

根据软土地层桥梁群桩基础的沉降特性，推导该地质环境下群桩模型试验相似法则，自行设计带承台群桩基础的室内模型并开展试验研究。试验结果表明：在桩身范围内，附加应力随深度衰减，在分布形式上，附加应力分布形式可近似为三角形；同时，桩侧土体的竖向应力随着桩项沉降的增加而相应的增加，在接近极限荷载产生较大沉降时也没有表现出明显收敛的现象；群桩在施加荷载时（不同施工阶段），桩周上部分土中产生较大的超静孔隙水压力，随着时间逐渐消散，即土体的固结过程需要一定时间；群桩的荷载与沉降关系明显呈现非线性特性，其尸_嗒曲线大致可以划分为线性阶段、屈服阶段和整体破坏阶段3个阶段：且通过试验可知卸载后，各群桩位移回弹很小，经外荷载作用后，产生较大的塑性变形，因而群桩沉降应作为桩基础设计控制条件之一。

英文摘要：

Based on the settlement characteristics of bridge pile foundation on soft soil stratum, the similarity rule of pile group model in this geological situation was derived. The indoor model of pile group foundation with pile cap was self-designed and analyzed. The test results show that the additional stress attenuates with the increase of depth and its distribution form approximates as triangular form within the scope of the pile body. At the same time, the vertical stress of pile-side soil increases as the settlement of pile top increases correspondingly. Moreover, the vertical stress of pile-side soil has not shown obvious converge even though the settlement of pile top is greater near the ultimate load. When the pile group foundation is under applied loads, representing different construction stages, the pile-side soil of upper pile body generates larger excess pore water pressure dissipating with time gradually, which indicates that the soil consolidation process needs some time to be finished. Furthermore, the relationship between load-settlement of pile group shows apparent non-linear characteristics, and its P-S curve can be divided into three stages of linear phase, yielding stage and the overall destruction phase. In addition, the displacement rebound of pile group is small during unloading because the pile group generates large plastic deformation after the external load is applied. Therefore, the settlement of pile group foundation is one of the control conditions in the pile foundation design.