刚性桩复合地基主要受力区和沉降变形源

The Main Stress Area and Settlement Deformation Source of Rigid Pile Composite Foundation

研究目的:本文对常用的几种附加应力计算模式进行梳理,分析了几种计算方法存在的不足。通过对刚性桩复合地基受力进行理论分析和受力模式简化,建立适合工程应用的附加应力计算模型,从而为准确把握地基土变形特征、变形部位、变形量,有效进行工后沉降控制提供依据。在此基础上,对刚性桩复合地基铁路路基的沉降变形源进行分析。研究结论:(1)铁路路基条件下,刚性桩复合地基的附加应力集中在下卧层,以及桩顶、桩底段,这些位置是地基的主要受力区;(2)在桩底以下1~2 m附加应力达到最大,最大值约为路堤荷载的0.7~0.9倍,自此向下下卧层中附加应力随深度衰减;(3)以条形均布荷载Mindlin解计算下卧层附加应力,以具有负摩阻的三角形摩阻力分布计算加固区附加应力的"并联-摩阻"模型可用于计算刚性桩复合地基中附加应力分布;(4)下卧层和桩底段土体压缩变形对地基总沉降的贡献最大,主要受力区域内的黏性土层是后期沉降的变形源;(5)本研究成果可用于铁路路基刚性桩复合地基设计和总沉降、工后沉降分析。

Research purposes:Through a systematic analysis of commonly used calculation models of additional stress,the shortcomings of several calculation methods are pointed out.Through theoretical analysis and simplification of stress model of rigid pile composite foundation,the calculation model of additional stress suitable for engineering application is established.It provides a method for accurately calculating the deformation characteristics,deformation and its position in foundation.Based on the calculation method,the settlement and deformation sources of rigid pile composite foundation railway subgrade are analyzed.Research conclusions:(1)Under the condition of railway subgrade,the additional stress of rigid pile composite foundation is concentrated in the underlying layer,pile top and pile bottom,which are the main stress areas of the foundation.(2)The maximum additional stress is 1~2 m below the pile bottom,which is about 0.7~0.9 times of the embankment load,from which the additional stress in the underlying layer decreases with the depth.(3)Mindlin solution of strip uniform load is used the"parallel-friction"model can be used to calculate the additional stress distribution in the rigid pile composite foundation.(4)The soil compression deformation of the underlying layer and the pile bottom section contributes the most to the total settlement of the foundation,and the cohesive soil layer in the main stress area is the deformation source of the later settlement.(5)The research results can be used to analyze and control the total settlement and post construction settlement of rigid pile composite foundation of railway subgrade.