浅海填方路堤下带帽PTC桩地基的数值分析研究

Numerical analysis of embankments on soft soils improved by the capped PTC piles

浅海填方路堤下带帽PTC桩复合地基是一个典型的三维问题,其涉及流固耦合和桩土相互作用等复杂问题。为按三维问题对路堤下带帽PTC桩复合地基与砂桩复合地基的远期性状进行对比,以蒲永高速为例,在工程现场取原状土样,验证修正剑桥模型参数,采用非线性有限元软件ABAQUS对蒲永高速浅海填方路堤下带帽PTC桩复合地基进行三维有限元分析。提出以剪切带来模拟桩土的相互作用,以修正剑桥模型来模拟软土固结的计算模型。研究结果表明:带帽PTC桩达到最终沉降的96%的时间比砂桩的缩短了56%的时间,差异沉降减少了34.4%,后期也较稳定,可不进行超载预压。但较于砂桩其路基土体固结慢,应力水平高。

Embankments on soft soils improved by the capped PTC piles is a typical3D problem.It includes thecomplicated problems such as fluid-structure coupling and pile-soil interaction.In order to analyze long termcharacteristics of PTC pile composite foundation and sand pile composite foundation under embankment form a3D prospective,this paper took the Pu Yong expressway as an example.The soil samples were taken at theengineering site,and the parameters of the modified Cambridge model were verified.The nonlinear finite elementprogram(ABAQUS)was employed to analyze the structural behavior of the embankments on soft soils improvedby the capped PTC piles.A calculating model was proposed,which used a shear zone to simulate the interactionbetween soil and pile and utilized the modified Cambridge model to simulate the consolidation of soft soil.Theresults show that the time when the capped PTC pile reaches96%of the final settlement is shortened by56%compared to corresponding time of the sand pile.The differential settlement decreases by34.4%,and the laterperiod is more stable.However,compared with the sand pile,the subgrade soil is consolidated slowly,and thestress level is high.