北京某地铁站基坑降水数值模拟与沉降研究

发布时间：2019-02-14 21:00

【摘要】：地铁车站基坑开挖几乎都涉及到地下水控制的问题。地铁车站多设置于繁华地区,地面情况复杂。水位变化将导致土体有效应力变化,产生固结沉降;降水形成的漏斗又导致影响范围内不同地点沉降量的差异。这种不均匀沉降对地下构筑物、管线、建筑物地基基础会产生不同程度的影响,使其变形甚至断裂,危害基坑施工和人民群众财产安全,造成重大损失。本文依托北京地铁3号线二期平安里站基坑降水工程,对工程降水技术及适用范围做了简要介绍,并详细说明了平安里站工程降水设计的流程和计算结果。首先对基坑降水引起地面沉降这一现象进行理论分析。介绍了渗流的运动和连续性方程,不同性质含水层的二维非稳定渗流微分方程及定解条件;介绍了结合质量守恒定律、渗流基本方程和饱和土有效应力理论的太沙基一维固结方程,比奥三维固结微分方程组及其二维形式。其次介绍了有限元数值模拟软件MIDAS/G TS的特性和应用范围,简要介绍建模流程。对建模过程中的土体本构模型选取,边界荷载的确定和渗流一应力全耦合分析的应用等关键问题进行深入分析。通过算例的数值模拟,研究土体的变形模量、水位降深、含水层的渗透系数的变化对地面沉降的影响。最后结合3号线二期平安里站工程实例搭建二维有限元模型,分析降水引起的渗流场变化,讨论软件中非稳定流模拟水头函数设置的合理性。在渗流模型的基础上搭建渗流一应力耦合分析模型对基坑降水导致的地面沉降进行分析,最大沉降量约为5mm;并初步预测降水引起的既有6号线平安里站主体结构底部地层的不均匀沉降,最大沉降量约为3mm,倾斜度为2.7e-0 5,具有一定的理论意义和实用价值。
[Abstract]:The excavation of subway station foundation pit almost involves the problem of groundwater control. Subway stations are mostly located in busy areas, the ground situation is complex. The change of water level will lead to the change of soil effective stress and the formation of consolidation settlement, and the difference of settlement amount between different sites in the affected area will be caused by the funnel formed by precipitation. This kind of uneven settlement will affect the underground structure, pipeline and foundation of the building to varying degrees, make it deform or even break, endanger the foundation pit construction and the safety of the people's property, and cause great losses. Based on the foundation pit dewatering project of Pinganli Station in the second phase of Beijing Metro Line 3, this paper briefly introduces the dewatering technology and applicable scope of the project, and explains in detail the design process and calculation results of the dewatering in Pinganli Station. Firstly, the phenomenon of ground subsidence caused by foundation pit dewatering is analyzed theoretically. The motion and continuity equation of seepage flow, the differential equation of two-dimensional unsteady seepage of aquifer with different properties and the conditions of definite solution are introduced. Combined with the law of conservation of mass, the basic equation of seepage flow and the effective stress theory of saturated soil, the one-dimensional consolidation equation of Terzaghi, the system of three dimensional consolidation differential equations of Biot and its two-dimensional form are introduced. Secondly, the characteristics and application scope of finite element numerical simulation software MIDAS/G TS are introduced, and the modeling flow is briefly introduced. The selection of constitutive model of soil mass, the determination of boundary load and the application of seepage and stress coupling analysis in the process of modeling are deeply analyzed. Through the numerical simulation of an example, the influence of the deformation modulus of soil, the depth of water level and the variation of permeability coefficient of aquifer on the ground settlement is studied. Finally, a two-dimensional finite element model is built based on the engineering example of Pinganli Station on Line 3. The variation of seepage field caused by precipitation is analyzed, and the rationality of setting up water head function of non-steady flow simulation software is discussed. Based on the seepage model, the seepage stress coupling analysis model is built to analyze the ground subsidence caused by foundation pit dewatering. The maximum settlement is about 5 mm. The uneven settlement at the bottom of the main structure of the existing Pinganli Station on Line 6 caused by precipitation is preliminarily predicted. The maximum settlement is about 3 mm and the slope is 2.7e-0 5, which has certain theoretical significance and practical value.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U231.3;TU463

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