刚性桩加固软弱地基上路堤的稳定性问题(Ⅰ)--存在问题及单桩条件下的分析

Stability of embankment on soft subgrade reinforced by rigid piles (Ⅰ)——background and single pile analysis

目前各类刚性桩在软土路基加固中已有较多应用。首先对复合抗剪强度极限平衡法存在的问题进行了分析。在此基础上,基于刚性桩的刚度及强度特征,采用三维有限差分方法和二维强度折减有限差分数值方法,针对刚性桩复合地基支承路堤的整体稳定分析,对单桩位于路堤下不同位置时的路堤稳定性进行了研究,并与传统复合抗剪强度极限平衡法稳定分析结果进行对比。结果表明,当路堤下单桩位于不同位置时,路堤填筑过程中桩土相互作用机理、桩的破坏形式及桩对路堤稳定的贡献机理不同,桩的刚度对路堤稳定存在显著影响。路堤趋于稳定破坏时,位于路堤下不同位置的刚性桩的弯曲破坏比剪切破坏更易于发生。对刚性桩加固路堤,复合抗剪强度极限平衡法不能反映不同位置单桩的破坏机理,将显著高估路堤稳定性。

Besides the commonly used sand columns,stone column and deep mixed columns,rigid piles such as plain concrete piles and reinforced concrete piles are introduced to improve the stability of embankment constructed on soft subgrade.The stability analysis of embankment on soft subgrade improved by rigid piles is performed by using 3D and 2D numerical methods.For the embankment with only one rigid pile,the results indicate that the failure mode,pile-soil interaction of single pile and its contribution to the stability of embankment highly depend on its location with respect to the embankment.When the embankment is approaching failure,the concrete piles and reinforced pile under the embankment tend to subject to bending failure rather than shear failure.The pile flexural stiffness has an important effect on the stability of embankment.Because it fails to consider the failure mechanism of single pile at different locations,the limit equilibrium method using composite shear strength will overestimate the embankment stability.