高速铁路软土路基桩网复合地基体系沉降分析及对策研究

发布时间：2018-03-29 17:25

本文选题：高速铁路路基　切入点：桩网复合地基　出处：《中国铁道科学研究院》2017年博士论文

【摘要】：沉降变形是高速铁路路基面临的主要问题,地基是沉降变形的主要来源,尤其是深厚软土地区。桩网复合地基是我国高速铁路的一种主要地基处理方式。桩网复合地基沉降的来源是多方面的,有加筋垫层的压缩与桩顶刺入变形、加固区压缩沉降、下卧层压缩及桩体下刺变形。在桩网复合地基体系中,对于加固区沉降变形研究较多,对于桩体的上穿及下刺问题尚缺乏可靠的分析和计算方法,整体沉降的内在规律还有待深入研究,而且对于高速铁路还存在精细计算与高精度控制的需求。本文开展高速铁路软土路基桩网复合地基体系沉降分析及对策研究。论文通过仿真计算和单桩模型试验,研究桩网复合地基垫层加筋体变形及失效机制以及不同条件下垫层变形的规律;通过模型试验,研究桩网复合地基荷载传递与变形特征,分析桩顶和桩底平面荷载分布特征及桩端上穿、下刺的变形规律;通过现场试验,分析单桩承载力以及桩侧摩阻力分布规律;系统研究桩网复合地基沉降计算模式和方法;针对桩网复合地基沉降变形问题,分析研究相应的整治对策。主要成果如下:(1)揭示了加筋垫层与桩端相互作用特征和变形规律,得出了垫层加筋体在桩顶和桩间位置的完整变形形态,以及区别于桩间悬索理论的加筋体应变最大位置,修正了现有加筋体拉力计算公式,提出了加筋垫层设计计算公式。(2)得出了桩网复合地基各部位沉降变形特征,基于膜式压力分布传感器测试,探明了桩顶与垫层、桩底与下卧层界面处连续的压力分布形态,分析提出了桩体上穿、下刺变形简化计算公式。(3)基于桩底应力分布情况,得出了桩底下卧层局部应力集中的深度影响范围,提出了下卧层沉降局部应力集中区和应力均布区分层计算方案。考虑垫层作用,对现有土拱结构形态进行了优化。(4)建立了适用于高速铁路桩网复合地基的综合沉降作用体系计算模型,并通过模型试验和现场试验,验证了其有效性。基于高速铁路桩网复合地基沉降特性,提出了针对不同部位沉降变形的整治措施。
[Abstract]:Settlement and deformation are the main problems faced by high-speed railway subgrade, and the foundation is the main source of settlement and deformation. Especially in deep soft soil area, pile-net composite foundation is one of the main ground treatment methods of high-speed railway in our country. The settlement of pile-net composite foundation comes from many aspects, including the compression of reinforced cushion and the deformation of pile top, and the compression settlement of reinforced zone. In the pile-net composite foundation system, there are many researches on the settlement and deformation of the strengthened area, and there is still no reliable analysis and calculation method for the problem of the top and bottom burr of the pile. The internal law of the whole settlement still needs to be deeply studied. There is also a need for fine calculation and high precision control for high-speed railway. In this paper, the settlement analysis and countermeasures of soft soil pile network composite foundation system of high speed railway are carried out, and the simulation calculation and single pile model test are carried out in this paper. The deformation and failure mechanism of cushion reinforcement in pile-net composite foundation and the law of cushion deformation under different conditions are studied, and the load transfer and deformation characteristics of pile-net composite foundation are studied by model test. The characteristics of the plane load distribution on the top and bottom of the pile and the deformation of the top and bottom of the pile are analyzed, the bearing capacity of the single pile and the distribution of the frictional resistance on the side of the pile are analyzed through the field test, and the settlement calculation model and method of the composite foundation with pile net are studied systematically. In view of settlement and deformation of pile-net composite foundation, the corresponding countermeasures are analyzed and studied. The main results are as follows: 1) revealing the interaction characteristics and deformation law between reinforced cushion and pile end. The complete deformation pattern of cushion reinforced body at the top of pile and the position between piles, and the maximum strain position of reinforced body, which are different from the theory of cable suspension between piles, are obtained, and the existing formulas for calculating the tensile force of reinforced body are revised. The calculation formula of reinforced cushion design is put forward. The settlement and deformation characteristics of various parts of pile-netted composite foundation are obtained. Based on the test of membrane pressure distribution sensor, the continuous pressure distribution patterns at the interface between the pile top and cushion, the interface between the pile bottom and the lower horizontal layer are found out. Based on the stress distribution at the bottom of the pile, the depth of the local stress concentration in the horizontal layer under the pile is obtained, and the influence of the depth of the stress concentration on the depth of the local stress concentration in the horizontal layer of the pile is obtained. In this paper, the calculation scheme of local stress concentration zone and uniform stress distribution of subhorizontal layer settlement is put forward, considering the effect of cushion, Based on the optimization of the existing soil arch structure, the calculation model of the comprehensive settlement system for the pile-net composite foundation of high-speed railway is established, and the model test and field test are carried out. Based on the settlement characteristics of pile-net composite foundation in high-speed railway, the measures for settlement and deformation of different parts are put forward.
【学位授予单位】：中国铁道科学研究院
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TU473.1

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