基坑开挖反压土时间效应机理分析

发布时间：2018-05-26 14:32

本文选题：蠕变 + Merchant模型　；参考：《天津大学》2014年硕士论文

【摘要】：蠕变是岩土材料重要的性质,软黏土的蠕变特性对工程结构的稳定和变形有着至关重要的影响,成为工程建设中需要考虑的重要问题之一。岩土蠕变模型种类复杂,参数繁多,蠕变模型及其参数辨识成为工程应用中亟需解决的问题。由于室内蠕变实验会耗费大量的人力、物力以及时间,实际操作中存在较多的困难,且土体蠕变试验并没有完整明确的土工试验规程,蠕变试验结果随意性较强。本文结合天津地区软黏土蠕变试验结果,采用回归拟合的方法确定适宜的本构模型及其参数,并用数值计算软件证明了拟合的正确性。大型的软土基坑一般开挖面积较大,从工期,造价和施工难度上往往难以施加对撑。根据最近的工程实例,开始采用基坑周边围护范围预留反压土的方案,可取的良好的经济效益。以往的反压土研究多集中于对围护结构的作用,并没有关注软黏土蠕变特性对反压土“围护体系”的影响机理。本文通过有限元计算探究分析了软黏土蠕变特性对于围护结构及基坑稳定变形的影响。深大基坑反压土开挖施工过程中,受到各种施工参数的影响,本文通过有限元分析软件建立了基本算例,分析了反压土截面性状、土体本构模型、基坑开挖速度、地下水渗流、土体应力历史等因素对反压土体系时间效应的影响,探究了反压土的时间效应机理,以期指导工程实践。最后结合天津嘉海一期实际工程建立有限元计算模型,探讨了反压土无支撑体系的时间效应。进一步证实了软黏土地区深大基坑施工过程中反压土体系的时间效应,分析了无支撑期间围护结构及基坑的受力及变形特征,揭示了基坑开挖反压土时间效应机理。
[Abstract]:Creep is an important property of geotechnical materials. The creep characteristics of soft clay have a vital effect on the stability and deformation of engineering structures, and become one of the important problems to be considered in engineering construction. The creep model of rock and soil is complicated and has a variety of parameters. The creep model and its parameter identification have become an urgent problem to be solved in engineering application. Because the indoor creep test will consume a lot of manpower, material resources and time, there are many difficulties in the actual operation, and there is no complete and definite geotechnical test rules for the creep test of soil, and the creep test results are random. Based on the creep test results of soft clay in Tianjin area, the suitable constitutive model and its parameters are determined by regression fitting method, and the correctness of the fitting is proved by numerical calculation software. The excavation area of large soft soil foundation pit is generally large, so it is difficult to apply bracing in terms of time limit, cost and construction difficulty. According to the recent engineering examples, the scheme of reserving backpressure soil in the surrounding retaining area of foundation pit is adopted, which is desirable for good economic benefit. In the past, the research of backpressure soil focused on the effect of the retaining structure, and did not pay attention to the influence mechanism of the creep characteristics of soft clay on the "envelope system" of the backpressure soil. In this paper, the influence of creep characteristics of soft clay on the stable deformation of retaining structure and foundation pit is analyzed by finite element method. During the excavation of deep and large foundation pit, it is affected by various construction parameters. In this paper, a basic example is established by means of finite element analysis software, and the cross section behavior of backpressure soil, constitutive model of soil, excavation speed of foundation pit and seepage of groundwater are analyzed. The influence of soil stress history and other factors on the time effect of backcompacted soil system is discussed, and the time effect mechanism of backcompacted soil is explored in order to guide engineering practice. Finally, the finite element model is established for the first stage of Tianjin Jia-hai Project, and the time effect of the unbraced soil system is discussed. The time effect of the backpressure soil system during the construction of deep and large foundation pit in soft clay area is further confirmed. The stress and deformation characteristics of the retaining structure and foundation pit during the period of no support are analyzed, and the mechanism of the time effect of the backpressure soil in the excavation of the foundation pit is revealed.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU753

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