路堤荷载下碎石桩复合地基荷载传递规律及沉降分析

发布时间：2018-04-06 23:30

本文选题：复合地基　切入点：碎石桩　出处：《湖南大学》2014年硕士论文

【摘要】：随着复合地基技术在地基处理中的广泛运用，其理论研究也正得到不断发展与完善。碎石桩复合地基作为高速公路软弱地基常用处治技术的一种，虽已有不少有关碎石桩复合地基承载力与沉降等方面的研究，但对其复杂加固机理与承载变形特性的了解仍不全面，如竖向荷载作用下桩土将发生相对滑移，且浅层软土区内的碎石桩体会发生径向鼓胀变形等，导致桩土体系受力并非简单的等应变模型，有必要探讨和建立更加切合实际情况的分析模型。同时，如何合理分析计算路堤荷载下碎石桩复合地基的沉降仍是目前的研究难点与重点。为此，本文基于已有研究成果，进一步探讨了路堤荷载下碎石桩复合地基的沉降分析方法，主要工作具体如下： (1)基于已有研究成果，探讨了碎石桩复合地基的加固机理、变形特性及其在竖向荷载作用下的破坏模式，并总结归纳出几种常见的路堤荷载下碎石桩复合地基承载力计算模式。 (2)通过引入更为合适的桩周土竖向与径向位移模式，并考虑桩-土相互作用、碎石桩的鼓胀变形，以及桩侧摩阻力分布存在中性点等因素，建立出桩身内力位移控制方程，进而导得了路堤荷载下碎石桩复合地基中桩侧摩阻力、桩身正应力以及桩周土体附加应力分布的解析解。在此基础上，引入相应的边界条件，进一步推导出桩身压缩量与加固区土体压缩量的简化计算公式，并给出了相应计算参数的确定方法。 (3)结合工程实例的对比分析结果表明：复合模量法高估了桩体的作用，且因不考虑碎石桩的径向鼓胀变形，导致沉降计算值低于实测值而偏于不保守；而基于本文方法的计算结果，较复合模量法更接近实测值，这是由于考虑了桩体鼓胀变形、桩-土相互作用及桩侧摩阻力分布中性点等实际受力变形特点。通过进一步的参数对比分析，探讨了路堤荷载下碎石桩复合地基桩身正应力与桩侧摩阻力的分布规律，，并获得了路堤高度、桩土模量比与泊松比、及面积置换率等参数对路堤荷载下碎石桩复合地基荷载传递的影响规律。
[Abstract]:With the extensive application of composite foundation technology in foundation treatment, its theoretical research is also being developed and perfected.Gravel pile composite foundation is one of the common treatment techniques for soft foundation of expressway. Although there have been many researches on bearing capacity and settlement of gravel pile composite foundation,However, the complex reinforcement mechanism and bearing deformation characteristics are still not fully understood, such as the relative slip of pile and soil under vertical load, and the radial bulging deformation of gravel pile in shallow soft soil area, etc.It is necessary to discuss and establish a more practical analysis model for pile-soil system.At the same time, how to reasonably analyze and calculate the settlement of gravel pile composite foundation under embankment load is still a difficult and important point.Therefore, based on the existing research results, this paper further discusses the settlement analysis method of gravel pile composite foundation under embankment load, the main work is as follows:1) based on the existing research results, the reinforcement mechanism, deformation characteristics and failure modes of gravel pile composite foundation under vertical load are discussed, and several common calculation models of bearing capacity of gravel pile composite foundation under embankment load are summarized.2) by introducing more suitable vertical and radial displacement models of soil around piles, considering the pile-soil interaction, swelling and deformation of gravel piles, and the neutral point of friction distribution on the side of piles, the governing equations of internal forces and displacements of piles are established.The analytical solution of pile side friction, normal stress of pile body and additional stress distribution of soil around pile in composite foundation of gravel pile under embankment load is obtained.On this basis, the simplified formulas for calculating the compression of pile body and the soil in the strengthened area are derived by introducing the corresponding boundary conditions, and the determination method of the corresponding calculation parameters is given.The results show that the composite modulus method overestimates the role of pile body and is not conservative due to the fact that the radial bulging deformation of gravel pile is not considered and the calculated settlement value is lower than the measured value.Based on the calculation results of this method, it is closer to the measured value than the composite modulus method, which is due to the consideration of the actual deformation characteristics such as the bulging deformation of the pile, the pile-soil interaction and the neutral point of friction distribution on the side of the pile.Through further comparison and analysis of parameters, the distribution of normal stress and lateral friction of gravel pile composite foundation under embankment load is discussed, and the height of embankment, pile-soil modulus ratio and Poisson's ratio are obtained.The influence of parameters such as area replacement ratio on load transfer of gravel pile composite foundation under embankment load.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U416.1

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