沉管隧道中设置褥垫层的钢管桩减沉机理研究

发布时间：2018-06-28 16:08

  本文选题：沉管隧道 + 减沉桩　； 参考：《东南大学》2015年博士论文

【摘要】：本文以国家科技支撑计划项目“港珠澳大桥跨海集群工程建设技术研究与示范”研究课题——“外海厚软基大回淤超长沉管隧道设计与施工关键技术”(项目编号：2011BAG07B01)为依托,针对港珠澳大桥沉管隧道底部减沉群桩基础,开展了大量文献调研,采用了理论分析、室内模型试验研究相结合的技术路线,较全面的研究了沉管荷载作用下钢管减沉群桩的承载特性。主要研究内容包括：带垫层减沉单桩及群桩沉降、桩土荷载分担比计算理论；基于均匀设计以及正交设计的沉管减沉桩承载性能模型试验及影响因素统计学分析；港珠澳大桥沉管隧道减沉群桩基础有限元数值模拟及相关参数影响研究；本文减沉桩计算理论在依托工程实际设计方案中的运用与分析。主要工作和结论如下：1)利用荷载传递法,提出了一种考虑了桩顶有无垫层对沉管隧道沉降影响的钢管减沉单桩计算理论。对于桩顶无垫层的工况,通过预先指定荷载分担比以明确桩土荷载,利用桩分段迭代计算求得减沉桩沉降。对于桩顶设置垫层的工况,提出了等效桩的概念,明确了桩顶与桩间土不同位置垫层的压缩计算方法,并基于刚性沉管底不同区域沉降协调,利用迭代计算得到桩土荷载分担比和减沉桩基沉降。2)基于荷载传递法得到的减沉桩侧摩阻力与端阻力,提出了采用弹性理论计算群桩沉降的带垫层减沉群桩混合法。通过分离桩土弹、塑性位移,提取了桩侧摩阻力弹性段,并对桩侧摩阻力分布进行等效线性化,然后进行不同区域侧摩阻力的Geddes应力解的叠加,推得了减沉桩桩端平面以下土层内任一深度处的竖向附加应力计算公式。通过基于群桩相互作用附加沉降与基桩受力协调、沉管底不同区域位移协调的原则,得到了适用于计算带垫层减沉群桩荷载分担比以及沉降的迭代计算方法。3)采用均匀设计方法完成6组初步模型试验,同时考虑了桩长、桩距、垫层厚度、桩帽等多种因素,每个因素大跨度的选择6个水平,以便覆盖工程所有可能的取值范围。通过试验数据分析和数理统计分析,得到多种因素共同作用下沉管沉降的基本规律,为后续模型试验确定参数,并为工程设计方法提供参考。提出经济性指标“单位面积用桩量”的概念,用于在众多的符合减沉或承载力要求的不同桩基组合中优选出最经济可行的基桩方案。通过对回归模型的反演分析,确定出一组符合沉降控制要求的最优减沉桩参数组合,且与试验结果吻合较好。4)基于混合正交试验设计的18组砂土中3x4群桩模型试验,分析了沉管荷载作用下沉管、垫层、钢管桩、地基土相互作用机理,揭示沉管底部土压力分布、不同位置桩身轴力分布及桩土荷载分担比等基本规律,以及它们随沉管荷载不同的变化规律。通过对沉管沉降和复合地基承载力做极差分析、方差分析和相关分析,进一步明确了桩距、桩长、垫层厚度及桩帽对沉管沉降以及减沉桩承载特性的影响。并通过单桩承载试验结果拟合得出荷载传递函数,结合本文提出的减沉桩计算理论对室内群桩试验的工况进行计算,结果与试验实测值进行对比。5)对实际工程三维有限元建模分析,建议减沉桩桩长采用30m左右；桩顶宜设置垫层,考虑到垫层过厚会增加沉降和成本,针对本工程建议取1m左右；在桩长及垫层厚度等参数确定的情况下,若要控制基础沉降,可在兼顾经济性的基础上适当减小桩间距,建议取用6D(D为桩间距)。6)利用本文提出的带垫层减沉单桩和群桩计算理论,针对港珠澳大桥沉管隧道底部减沉桩基础的某设计方案进行了单桩受力、群桩相互作用等计算分析,得到了本工程合理的桩土荷载分担比及沉管总刚度。此外,计算了减沉桩基极限承载力,并与本文提出的减沉桩承载计算理论所得的减沉桩荷载值进行对比,为工程设计施工提供参考。综上所述,本文针对港珠澳大桥沉管隧道减沉桩基础的工程特点,深入研究减沉桩沉降以及桩土荷载分担比计算理论,并通过模型试验对相关减沉桩承载影响因素加以研究,以达到应用于实际工程、解决实际问题的目的。
[Abstract]:Based on the national science and technology support project "the research and demonstration of the technical research and demonstration of the construction of the harbour Zhuhai Macao Bridge across the sea cluster Engineering" - "the key technology of the design and construction of the overlong immersed tube tunnel with thick soft foundation and large back siltation" (project number: 2011BAG07B01), this paper aims at the foundation of the sinking group pile foundation at the bottom of the immersed tunnel tunnel of the Hong Kong Zhuhai Macao Bridge. A large amount of literature survey was carried out. The bearing characteristics of the pile under immersed tube loading were studied comprehensively by the theoretical analysis and the technical route combined with the indoor model test. The main research contents include the theory of calculation of the pile settlement and the load sharing ratio of pile and soil, based on the uniform design and the positive method. The bearing performance model test and the influence factor analysis of the immersed tube sinking pile, the finite element numerical simulation of the sinking group pile foundation of the immersed tunnel of Hong Kong Zhuhai Macao Bridge and the influence of related parameters; the application and analysis of the calculation theory of the settlement of the sinking pile in the actual design of the project. The main work and conclusion are as follows: 1) With the load transfer method, a calculation theory of steel pipe sinking single pile is proposed, which considers the effect of the pile top with or without the cushion on the settlement of the immersed tube tunnel. For the working condition of the pile top without the cushion, the settlement of the settlement of the pile is obtained by the specified load sharing ratio in order to clear the pile and soil load, and the pile subsection iteration calculation is used to set the cushion of the pile top. Based on the concept of equivalent pile, the compression calculation method for different position cushion of pile top and soil is clarified. Based on the settlement and coordination of different regions in the bottom of the rigid immersed tube, the lateral friction resistance and end resistance of the pile under the load transfer method are obtained by the iterative calculation and the load transfer method is used to obtain the side friction resistance and end resistance of the sinking pile based on the load transfer method. The elastic theory is put forward by using the load transfer method. In this paper, the mixing method of pile foundation subsidence reduction group pile is calculated. By separating pile soil elastic and plastic displacement, the elastic section of pile side friction is extracted, and the distribution of friction resistance of pile side is linearized. Then, the superposition of Geddes stress solution of side friction resistance in different regions is superimposed, and any depth in the soil layer below the end plane of the pile sinking pile is obtained. The formula for calculating the vertical additional stress. Based on the principle of coordination between pile group interaction and the stress of pile foundation, the principle of displacement coordination in different regions of the bottom of the immersed tube bottom, a method of calculating the load sharing ratio of pile sinking group piles and the iterative calculation method.3 for settlement is obtained. The 6 sets of preliminary model tests are completed by the uniform design method. A variety of factors such as pile length, pile distance, cushion thickness, pile cap and so on, each factor is selected 6 levels for large span, in order to cover all possible range of value of the project. Through the analysis of experimental data and mathematical statistics analysis, the basic rules of sinking pipe settlement under the joint action of a variety of factors are obtained, and the parameters are determined for the follow-up model test and the engineering design is designed. The concept of economic index "per unit area pile amount" is proposed, which is used to optimize the most economical and feasible foundation pile scheme in a large number of different pile foundation combinations which conform to the requirement of reducing or bearing capacity. It is in good agreement with the test results.4) the 3x4 group pile model test of 18 groups of sand soil based on the mixed orthogonal experimental design, analyses the interaction mechanism of immersed tube, cushion, steel pipe pile and foundation soil under the effect of immersed tube load, reveals the distribution of soil pressure at the bottom of the immersed tube, the distribution of axial force of pile body in different positions and the ratio of pile and soil load, as well as them. The influence of pile spacing, pile length, cushion thickness and pile cap on the settlement of immersed tube and bearing characteristics of sinking piles is further clarified through the difference analysis, variance analysis and correlation analysis on the settlement of immersed tube and the bearing capacity of composite foundation, and the load transfer function is fitted through the test results of single pile bearing. The calculation theory of pile reduction pile calculation in this paper is used to calculate the working conditions of indoor pile group test, and the result is compared with the test measured value.5). It is suggested that the pile length of the pile should be about 30m, and the pile top should be set up. Considering that the cushion is too thick, the settlement and cost will be increased, and the proposal of 1m for this project is taken. In the condition of determining the pile length and the thickness of the cushion, in order to control the foundation settlement, the pile spacing can be reduced properly on the basis of the economy, and it is suggested to use the 6D (D as the pile spacing).6) to use the theory of pile sinking single pile and group pile proposed in this paper, and the foundation of the foundation of the sinking pile foundation at the bottom of the immersed tunnel tunnel of Hong Kong Zhuhai Macao Bridge is given. The design scheme has carried on the calculation and analysis of single pile force, pile group interaction and so on. The reasonable load sharing ratio of pile and soil and the total stiffness of the immersed tube are obtained. In addition, the ultimate bearing capacity of the pile foundation is calculated. It is compared with the load value of the settlement pile of the pile bearing calculation theory proposed in this paper, which provides a reference for the engineering design and construction. To sum up, in view of the engineering characteristics of the sinking pile foundation of the immersed tube tunnel of the Hong Kong Zhuhai Macao Bridge, this paper deeply studies the calculation theory of settlement and load sharing ratio of the pile and soil, and studies the influence factors of the bearing capacity of the related settlement pile through the model test in order to achieve the purpose of applying to the actual engineering and solving the practical problems.
【学位授予单位】：东南大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U459.5
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本文编号：2078571