CFG桩复合地基固结与沉降分析及数值模拟

发布时间：2018-06-07 18:22

本文选题：CFG桩复合地基 + 固结　；参考：《湖南大学》2014年硕士论文

【摘要】：近年来复合地基技术在地基处理中得到了广泛应用，复合地基理论也成为了岩土工程领域重要的研究课题。CFG桩(水泥-粉煤灰-碎石桩的简称)复合地基作为其中的一种常用技术，具有施工简单、质量可靠和成本低等优点，用于软基处治时，可显著提高地基承载力，减少其沉降，并能变废(粉煤灰)为宝，经济和社会效益明显。但目前有关CFG桩复合地基的理论研究整体上仍落后于其工程实践，特别是对深厚软土中未打穿CFG桩复合地基(由桩长范围的加固区和桩长以下的下卧层组成)的研究更是鲜见报道。为此，本文进一步探讨了未打穿CFG桩复合地基的固结和沉降特性，并完成了数值模拟分析，具体工作主要如下：首先，结合复合地基及CFG桩复合地基的已有研究基础和发展现状，针对CFG桩复合地基的承载变形性状、作用机理、褥垫层设置、承载力确定及设计计算方法等方面，进行了较为系统深入的讨论和分析。其次，将未打穿CFG桩复合地基简化为双层地基，，基于双层地基一维固结理论，考虑桩体渗透和不渗透两种情况，分别建立出未打穿CFG桩复合地基的固结方程，通过引入相应的边界条件，导得了不同工况下按沉降与按孔压定义的未打穿CFG桩复合地基固结度计算公式。在此基础上，基于MATLAB编制出相应的计算程序，进而分析了桩长、桩体压缩模量、桩体贯入比和面积置换率等参数对于固结过程的影响规律，并证实了“对于未打穿复合地基，按沉降定义的固结度不等于按孔压定义的固结度”这一结论。第三，基于所导得的未打穿CFG桩复合地基固结度计算公式，由固结度的定义，得到了考虑时效性的CFG桩复合地基的沉降计算公式，并通过算例对比分析，验证了本文方法的可行性。最后，基于FLAC3D软件平台，建立了未打穿CFG桩复合地基的三维数值分析模型，通过改变几何力学参数进行对比分析，获得了荷载水平、桩间土体模量、下卧层土体模量和桩长等参数对未打穿CFG桩复合地基沉降的影响规律曲线，可供工程实践参考。
[Abstract]:In recent years, composite foundation technology has been widely used in foundation treatment. The theory of composite foundation has also become an important research subject in geotechnical engineering field. As a common technology, CFG pile (short for cement-flyash gravel pile) composite foundation has the advantages of simple construction, reliable quality and low cost. When used in soft foundation treatment, the bearing capacity of the foundation can be significantly increased, its settlement can be reduced, and the waste (fly ash) can be changed into a treasure. The economic and social benefits are obvious. However, at present, the theoretical research on CFG pile composite foundation is still lagging behind its engineering practice. Especially, the study of CFG pile composite foundation (composed of the reinforcement zone in the long range of pile and the lower horizontal layer below the pile length) in the deep soft soil is rarely reported. Therefore, this paper further discusses the consolidation and settlement characteristics of CFG pile composite foundation, and completes the numerical simulation analysis. The main work is as follows: first, Combined with the existing research foundation and development status of composite foundation and CFG pile composite foundation, aiming at the bearing deformation behavior, action mechanism, cushion setting, bearing capacity determination and design calculation method of CFG pile composite foundation, etc. Then, the CFG pile composite foundation is simplified as a double-layer foundation. Based on the one-dimensional consolidation theory of the double-layer foundation, the seepage and impermeability of the pile body are considered. The consolidation equations of CFG pile composite foundation without penetration are established respectively. By introducing the corresponding boundary conditions, the formulas for calculating the consolidation degree of CFG pile composite foundation under different working conditions are derived according to the definition of settlement and pore pressure. On this basis, the corresponding calculation program based on MATLAB is worked out, and the influence of pile length, pile compression modulus, pile penetration ratio and area replacement ratio on the consolidation process is analyzed. The conclusion that the degree of consolidation defined by settlement is not equal to the degree of consolidation defined by pore pressure ". Third, based on the derived formula for calculating the degree of consolidation of CFG pile composite foundation, the definition of consolidation degree is derived from the definition of consolidation degree. The formula for calculating the settlement of CFG pile composite foundation considering time effect is obtained, and the feasibility of this method is verified by comparison and analysis of examples. Finally, based on the software platform of FLAC3D, The three-dimensional numerical analysis model of CFG pile composite foundation is established. By changing the geometric mechanical parameters, the load level and the soil modulus between piles are obtained. The influence of soil modulus and pile length on the settlement of CFG pile composite foundation can be used as a reference for engineering practice.
【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】：TU470

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