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对京沪高速铁路CFG(Cement Fly-ash Gravel)桩筏复合地基进行了现场试验研究,实测了桩顶、两桩中心、四桩中心处桩间土体的沉降值及路基面沉降值,深入分析了桩顶、两桩中心、四桩中心处桩间土体的沉降及路基面沉降随荷载和固结时间的变化规律,对CFG桩筏复合地基的沉降特性进行深入研究,得到以下主要结论:沉降主要发生在加载期间,即沉降快速发展阶段,期间桩顶、桩间土沉降均占总沉降的60%左右;CFG桩加固区沉降约占相应总沉降的1/4,下卧层沉降约占3/4;路基面沉降曲线成锅形分布,路基中间沉降量较大,路基两侧较小;地基沉降—荷载—时间规律可分为3个阶段,即沉降快速发展阶段、沉降发展阶段和沉降基本稳定阶段;超载预压对于减少工后沉降是必要的,预压3个月后,地基沉降基本上趋于稳定,路堤的预压静置时间应不小于3个月。
Field tests were carried out on the piled raft composite foundation of CFG (Cement Fly-ash Gravel) in Beijing-Shanghai high-speed railway. The settlement of subsoil and the settlement of subgrade at the center of piles, two centers and four piles were measured. The settlement of subsoil, the settlement of subgrade between four piles and the load and consolidation time of subgrade are analyzed. The settlement characteristics of CFG piled raft composite foundation are deeply studied, and the following main conclusions are obtained : Subsidence occurred mainly during the loading period, that is, the stage of rapid development of settlement, during which the settlement of the pile top and the pile accounted for about 60% of the total settlement. The settlement of the CFG pile reinforcement zone accounted for about 1/4 of the corresponding total settlement and the subsidence settlement About 3/4; subgrade surface subsidence curve into a pot-shaped distribution, subgrade settlement in the middle of the larger, smaller on both sides of the roadbed; subsidence-load-time law can be divided into three stages, namely rapid settlement of the stage of development, settlement development Stage and subsidence basically stable stage; Overloading preloading is necessary to reduce post-construction settlement, preloading 3 months later, the foundation settlement basically stabilized, the embankment preloading time should not be less than 3 months.