带帽有孔管桩群桩复合地基工作性状试验研究

发布时间：2018-03-20 14:01

本文选题：有孔管桩　切入点：群桩　出处：《南昌航空大学》2017年硕士论文　论文类型：学位论文

【摘要】：对于高速公路、高速铁路等工程的深厚软土地基,目前国内外很多都是通过选用合适的竖向增强体形成复合地基进行地基处理,以达到减少建筑物沉降、提高地基承载力的目的。带帽管桩复合地基适合于较为深厚的软土地基处理,但在静压管桩沉桩过程中所产生的挤土效应可能会造成邻桩桩身移位、上浮、倾斜,甚至断桩等不良后果。为此,课题组提出了带帽有孔管桩复合地基技术。当前对带帽有孔管桩复合地基技术的研究主要集中在有孔管桩单桩承载性状,对有孔管桩群桩的工作性状研究尚处于一片空白,但实际工程中使用更多的却是群桩。因此,对带帽有孔管桩群桩复合地基的工作性状研究,具有一定的必要性和实践意义。本文通过室内模型试验和数值模拟两种方法,对带帽有孔管桩群桩复合地基的工作性状进行了研究与探讨。主要研究内容及成果如下:(1)对有孔管桩群桩沉桩时引起的超孔隙水压力进行了室内模型试验研究。结果表明,有孔管桩群桩沉桩产生的超孔隙水压力不是单桩沉桩产生的超孔隙水压力简单叠加,而是单桩相互影响的累积和消散的综合结果,且有孔管桩群桩测点产生的超孔隙水压力与沉桩方向有关,当沉桩方向趋向测点时,有孔管桩群桩产生的超孔隙水压力上升,当其背向测点时超孔隙水压力下降。另外,星状布孔方式的有孔管桩群桩沉桩产生的超孔隙水压力峰值最小、消散速率最快,最有利于减小沉桩挤土效应,沉桩效应最佳。桩壁开孔方式为管桩群桩施工时,如何减小沉桩挤土效应提供了一种新的途径。(2)对竖向荷载下带帽有孔管桩群桩复合地基的工作性状进行了室内模型试验研究。结果表明,带帽有孔管桩群桩复合地基沉降量小于带帽无孔管桩群桩复合地基沉降量,即带帽有孔管桩群桩复合地基的控沉能力比带帽无孔管桩群桩复合地基的控沉能力强;群桩桩身轴力随深度的增加而减少,且随竖向荷载的增大,轴力减少的速率逐渐增大;在加载初期,荷载主要由桩体承担,随荷载继续增加,荷载由桩土共同承担,直至达到桩土共同工作的稳定状态。另外,随荷载等级逐渐加大,带帽有孔管桩群桩复合地基桩土应力比始终小于带帽无孔管桩群桩复合地基桩土应力比,这进一步说明了桩身开孔能增强管桩群桩复合地基土体承载力。(3)采用ABAQUS软件,对带帽有孔管桩群桩复合地基的工作性状进行了数值模拟分析,并与室内试验研究结果进行对比,结果证实了室内模型试验结果是正确的。
[Abstract]:For the deep soft soil foundation of expressway, high-speed railway and other projects, at present, many of the domestic and foreign foundation are treated by selecting suitable vertical reinforcement to form composite foundation, so as to reduce the settlement of buildings. The purpose of improving the bearing capacity of foundation is that the composite foundation with cap pipe pile is suitable for deep soft soil foundation treatment, but the squeezing effect of static pressure pipe pile in the course of piling may result in the displacement of adjacent pile body, the floating, and the inclination of pile body. For this reason, we put forward the technology of composite foundation with cap and perforated pipe pile. At present, the research on the composite foundation technology of pipe pile with cap is mainly focused on the bearing behavior of single pile with hole pipe pile. The study on the working behavior of the pile group with holes is still blank, but it is more often used in practical engineering. Therefore, the working behavior of the pile group with cap is studied. It has certain necessity and practical significance. This paper adopts two methods: indoor model test and numerical simulation. In this paper, the working behavior of pile group foundation with cap is studied and discussed. The main research contents and results are as follows: 1) the laboratory model test of excess pore water pressure caused by pile group pile with hole pile is carried out. The results show that, The excess pore water pressure caused by pile group piling with holes is not a simple superposition of excess pore water pressure produced by single pile driving, but a comprehensive result of accumulation and dissipation of single pile interaction. And the excess pore water pressure produced by the pile group pile group is related to the direction of piling. When the pile driving direction tends to the measuring point, the excess pore water pressure of the pile group increases, and the excess pore water pressure decreases when the pile is measured in the back direction. The maximum value of excess pore water pressure and the fastest dissipation rate of the pile-driven pile with holes in the star-arranged hole mode are the minimum and the quickest, which is most helpful to reduce the pile-squeezing effect and the pile-driving effect is the best. The hole opening mode of the pile wall is the pipe pile group pile group construction. How to reduce the compaction effect of pile-sinking is a new way to study the working behavior of pile-group composite foundation with cap hole pile under vertical load. The results show that the experimental results are as follows: (1) the experimental results are as follows: (1) A new way to reduce the compaction effect of pile-driven piles is provided. The settlement of pile group with cap is smaller than that of pile group with cap, that is, the control ability of pile group with cap is better than that of pile group with cap. The axial force of group pile body decreases with the increase of depth, and with the increase of vertical load, the rate of axial force decrease increases gradually, at the beginning of loading, the load is mainly borne by pile body, and with the increase of load, the load is shared by pile and soil. In addition, with the increasing of load grade, the pile-soil stress ratio of pile with cap pile group pile group composite foundation is always smaller than that of pile soil composite foundation without hole pile group pile group foundation with cap, and the pile-soil stress ratio of pile and soil composite foundation with cap hole pile group pile group foundation is smaller than that with cap hole pile group pile group pile composite foundation. This further shows that the hole opening of pile body can enhance the bearing capacity of soil in the composite foundation of pipe pile group pile group. Using ABAQUS software, the numerical simulation analysis of the working behavior of the composite foundation of pipe pile group pile with cap is carried out, and the results are compared with the results of laboratory test. The results show that the results of indoor model tests are correct.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

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