中文摘要：

探究柔性基础下复合地基的沉降特性及规律，为以沉降控制的高填方堤坝下复合地基的设计和施工提供参考。以某路堤下复合地基为例，通过在桩土之间设置接触单元来考虑桩土间的相对位移，用“单元生死”技术模拟复合地基施工过程，运用ADINA软件对复合地基进行了沉降特性有限元分析。在不加载情况下，将数值计算的沉降结果与实际测量的沉降结果进行了对比，验证了数值模型的正确性。预测了加载情况下，地基沉降的进一步发展规律，考虑了桩土模量比、垫层和基础、施工工序对柔性基础下复合地基沉降的影响。计算结果表明：运行荷裁下地基沉降规律与不加栽时基本一致；垫层有协调桩土沉降的作用；不同施工工序下地基沉降规律有着很大差异。因此，对于柔性基础下复合地基，应设置0．2～0．3m的垫层，使桩体模量比n为10～50，采用“先土后桩”的施工工序以满足沉降控制要求。

英文摘要：

Research is done on the settlement of composite ground under flexible foundations to provide some references for the design and construction of composite ground under high embankment controlled by settlement. Taking one composite ground under high embankment for example, a contact model is established to describe relative displacement of piles and soil. The ＂cell life death decay＂ technique is used to simulate work progress, explore the settlement characteristics of composite foundation by the finite element soft ware ADINA. Under unload conditions, the settlement gained from measured value is compared with numerical computation, proved the correctness of calculation model. Forecasted the further development of ground settlement under load conditions. The influence of pile soil modulus ratio, cushion and foundation, construction process to settlement of composite ground under flexible foundation are analyzed. The calculation results show that： settlement of ground after loading has the same regulation with unload; cushion can coordinate settlement of pile and soil; settlement regularity has a great diversity in different construction processes. As for composite ground under flexible foundations, cushions with 0.2-0. 3 m should be set, pile-soil ratio between 10-20 should be determined, and ＂filling-piling＂ construction process should be chosen to meet the settlement control requirement.