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通过在上海S32高速公路某桥头处理段开展长短桩组合型复合地基现场试验,研究路堤填筑过程以及堆载预压期内桩土应力比、分层沉降、桩顶面和桩间土表面沉降、孔压等工程性状的变化规律;采用三维有限元法进行拓展研究,对比分析长短桩组合型复合地基与等长桩复合地基的加固机理。研究结果表明:随着路堤填土高度的增加,长桩和短桩的桩土应力比均逐渐增大并趋于稳定,稳定时长桩和短桩的桩土应力比分别为7～10和3～5;桩顶面和桩间土表面的沉降主要发生在填土期,预压期内沉降趋于稳定;总桩长相同的条件下,长短桩组合型复合地基加固效果优于等长桩复合地基,且存在持力层时的层状地基更利于长短桩组合型复合地基性能的发挥。
Through the field test of composite piles with long and short piles at a bridgehead section of Shanghai S32 expressway, the embankment filling process and pile-soil stress ratio, stratified settlement, pile top surface and soil surface settlement between piles during embankment preloading , Pore pressure and other engineering characteristics of the variation; using three-dimensional finite element method to expand the study, comparative analysis of long and short pile composite foundation and equal length pile composite foundation reinforcement mechanism. The results show that with the increase of embankment height, the pile-soil stress ratio of long pile and short pile increases gradually and tends to be stable. The pile-soil stress ratio of stable long pile and short pile is 7-10 and 3 respectively ~ 5. The settlement of the soil surface between pile top and piles mainly occurs during the filling period, and the settlement tends to be stable during the pre-compression period. Under the same total pile length, the reinforcement effect of the composite foundation with long and short piles is better than the equivalent length piles Composite foundation, and the presence of the stratum when the layered foundation is more conducive to the performance of long-short pile composite foundation.