【摘要】：地鐵車站基坑開挖幾乎都涉及到地下水控制的問題。地鐵車站多設(shè)置于繁華地區(qū),地面情況復(fù)雜。水位變化將導(dǎo)致土體有效應(yīng)力變化,產(chǎn)生固結(jié)沉降;降水形成的漏斗又導(dǎo)致影響范圍內(nèi)不同地點沉降量的差異。這種不均勻沉降對地下構(gòu)筑物、管線、建筑物地基基礎(chǔ)會產(chǎn)生不同程度的影響,使其變形甚至斷裂,危害基坑施工和人民群眾財產(chǎn)安全,造成重大損失。本文依托北京地鐵3號線二期平安里站基坑降水工程,對工程降水技術(shù)及適用范圍做了簡要介紹,并詳細說明了平安里站工程降水設(shè)計的流程和計算結(jié)果。首先對基坑降水引起地面沉降這一現(xiàn)象進行理論分析。介紹了滲流的運動和連續(xù)性方程,不同性質(zhì)含水層的二維非穩(wěn)定滲流微分方程及定解條件;介紹了結(jié)合質(zhì)量守恒定律、滲流基本方程和飽和土有效應(yīng)力理論的太沙基一維固結(jié)方程,比奧三維固結(jié)微分方程組及其二維形式。其次介紹了有限元數(shù)值模擬軟件MIDAS/G TS的特性和應(yīng)用范圍,簡要介紹建模流程。對建模過程中的土體本構(gòu)模型選取,邊界荷載的確定和滲流一應(yīng)力全耦合分析的應(yīng)用等關(guān)鍵問題進行深入分析。通過算例的數(shù)值模擬,研究土體的變形模量、水位降深、含水層的滲透系數(shù)的變化對地面沉降的影響。最后結(jié)合3號線二期平安里站工程實例搭建二維有限元模型,分析降水引起的滲流場變化,討論軟件中非穩(wěn)定流模擬水頭函數(shù)設(shè)置的合理性。在滲流模型的基礎(chǔ)上搭建滲流一應(yīng)力耦合分析模型對基坑降水導(dǎo)致的地面沉降進行分析,最大沉降量約為5mm;并初步預(yù)測降水引起的既有6號線平安里站主體結(jié)構(gòu)底部地層的不均勻沉降,最大沉降量約為3mm,傾斜度為2.7e-0 5,具有一定的理論意義和實用價值。
[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.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U231.3;TU463

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