桩-筏复合地基在高速铁路软土地基处理中所占比例较大,研究其变形特性对工程设计及运营期维修具有重要意义.基于沪宁(上海-南京)城际铁路PHC桩-筏复合地基和CFG桩-筏复合地基工程实例,采用室内模型试验和现场测试相结合的方法,对PHC和CFG桩-筏复合地基建设期及运营期变形特性进行研究.研究结果表明:若桩长和面积置换率相同,桩刚度对桩顶沉降影响较小;若桩刚度相同,桩顶沉降随面积置换率增加而减小;PHC桩-筏复合地基整体变形小于CFG桩-筏复合地基,且在限制侧向位移方面表现出较大的优越性;桩-筏复合地基在建造期(铺轨前)堆载预压3个月完成的沉降量约占堆载预压6个月沉降量的90％以上,约占铺轨后沉降量的80％,建造期沉降量约为运营后3年半沉降量的65.4％～78.6％.%Piled-raft composite foundation accounts for a large proportion of high speed railway soft foundation and the study on its deformation characteristics is of great significance for its engineering design and operation maintenance.Based on the engineering example of PHC piled-raft composite foundation and CFG piled-raft composite foundation of Shanghai-Nanjing intercity railway,the method of combining laboratory model test and in-situ test was adopted to study the deformation characteristics of the PHC and CFG piled-raft composite foundation in construction and operation period.The results show : if the pile length and area replacement ratio are the same,the effect of the pile stiffness on the settlement of pile top is little;if the pile stiffness stays the same,the settlement of pile top decreases with the increase of area replacement ratio;the overall deformation of PHC piled-raft composite foundation is smaller than that of the CFG and shows a greater superiority to CFG in limiting the lateral displacement;during the construction period(before laying the tracks),the settlement of piled-raft composite foundation under 3-month preloading accounts for more than 90％of the settlement under 6-months preloading,and 80％of the settlement after laying the tracks;the settlement in construction period accounts for about 65.4％～78.6％of the settlement after 3.5 years' operation.
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