软土地基上大尺寸模袋砂围堰稳定性分析

发布时间：2018-04-11 15:24

本文选题：大尺寸模袋砂围堰 + 软土地基　；参考：《华南理工大学》2016年硕士论文

【摘要】：模袋砂围堰的理论分析、试验研究远滞后于工程实践,工程上迫切需要对模袋砂围堰相关问题给出更多合理解答。目前关于模袋砂围堰的文献屡屡见刊,然而,多局限于单个或者多个模袋充填物力学特性的研究,或模袋砂围堰施工工艺的介绍,关于模袋砂围堰稳定性的研究,基本都是将模袋砂围堰等效成均质土,然后采用边坡稳定性分析手段计算其整体稳定安全系数。此法应用于坚硬地基上模袋砂围堰尚可满足工程要求,然而,软土地基上模袋砂围堰极限状态下表现为地基土侧向挤出,其本质是地基土的失稳破坏,继续采用边坡稳定性分析方法已失偏颇。因此,本文从地基承载力问题入手,采用数值分析手段基于强度折减理论对软土地基上大尺寸模袋砂围堰地基稳定性展开相关研究。首先,归纳总结了目前模袋砂围堰在国内外的研究现状以及该领域尚待研究的问题,并在此基础提出本文的研究课题及所采用的研究手段。采用大型有限元分析软件Abaqus建立了天然软土地基上大尺寸模袋砂围堰的数值模型,基于强度折减理论分析了软土地基上大尺寸模袋砂围堰的变形特性及稳定性规律,并对比了极限状态下天然软土地基上大、小尺寸模袋砂围堰地基破坏时的差异表现,而后通过敏感性分析,研究了围堰坡比及地基淤泥层厚度对围堰地基稳定性规律的影响,得到了一系列结论。依次建立反压平台护脚、水泥土搅拌桩加固软土地基及真空联合模袋砂堆载预压加固软土地基的数值分析模型,分析了三种不同加固方法下大尺寸模袋砂围堰地基的稳定性规律,并得到了相应结论。基于极限平衡理论,结合大尺寸模袋砂围堰自身的特点——围堰截面大,当地基发生整体滑动剪切破坏时,围堰地基下刚性核宽度小于大尺寸模袋砂围堰的等效宽度(模袋砂围堰顶宽跟底宽的平均值)——推导了天然软土地基上大尺寸模袋砂围堰地基的极限承载力计算公式。最后,基于弹性地基有限长梁理论推导了软土地基上大尺寸模袋砂围堰的模袋最大弯曲拉应力近似解析解的表达式。
[Abstract]:The theoretical analysis and experimental study of the sand cofferdam for moulding bags lag far behind the engineering practice. It is urgent to give more reasonable solutions to the problems related to the sand cofferdam in the mould bag.At present, the literatures on sand cofferdam of moulded bag are frequently published, however, most of them are limited to the study of mechanical properties of single or multiple filling materials, or the introduction of construction technology of sand cofferdam of mould bag, and the study of stability of sand cofferdam with mould bag.The sand cofferdam is basically equivalent to homogeneous soil, and then the overall stability safety factor is calculated by means of slope stability analysis.The application of this method to the sand cofferdam on the hard foundation can meet the engineering requirements. However, the ultimate state of the sand cofferdam on the soft foundation is lateral extrusion of the foundation soil, which is essentially the instability failure of the foundation soil.It is unbiased to continue to use slope stability analysis method.Therefore, starting with the bearing capacity of foundation, this paper studies the stability of large size sand cofferdam foundation on soft soil foundation based on strength reduction theory by means of numerical analysis.Firstly, this paper summarizes the current research situation of the sand cofferdam at home and abroad and the problems that need to be studied in this field, and puts forward the research topics and the research methods adopted in this paper.The numerical model of large size sand cofferdam on natural soft soil foundation is established by using the large finite element analysis software Abaqus. Based on the strength reduction theory, the deformation characteristics and stability of large size sand cofferdam on soft soil foundation are analyzed.The difference between the large and small size sand cofferdam foundation under the limit state is compared, and the influence of the slope ratio of cofferdam and the thickness of silt layer on the stability of cofferdam foundation is studied by sensitivity analysis.A series of conclusions have been drawn.The numerical analysis model of the soft soil foundation strengthened by cement soil mixing pile and the soft soil foundation strengthened by sand load preloading of vacuum combined mold bag is established in turn.The stability law of large size sand cofferdam foundation under three different reinforcement methods is analyzed, and the corresponding conclusions are obtained.Based on the limit equilibrium theory, combined with the characteristics of the large size sand cofferdam in the mold bag, the cofferdam has a large section, when the whole sliding shear failure occurs on the foundation,The width of rigid core under cofferdam foundation is smaller than the equivalent width of large size sand cofferdam (the average width of top width and bottom width of sand cofferdam). The formula of ultimate bearing capacity of large size sand cofferdam foundation on natural soft soil foundation is derived.Finally, based on the theory of finite long beam on elastic foundation, the approximate analytical solution of the maximum bending tensile stress of large size sand cofferdam on soft soil foundation is derived.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TV551.3

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