本文選題：不均勻沉降　切入點：路基拓寬　出處：《長安大學》2014年碩士論文

【摘要】：隨著國民經(jīng)濟高速持續(xù)不斷地發(fā)展，高速公路建設(shè)的也進入了快速發(fā)展的快車道，里程不斷增多，質(zhì)量也越來越優(yōu)良；然而我國在上個世紀末所修建的高速公路到現(xiàn)在交通流量已經(jīng)趨于飽和，大多都是四車道道路，道路服務(wù)也是大不如前，對其進行拓寬改造是勢在必行。但是，在拓寬后因為新老路基施工時間的差異以及路基本身特性的偏差，使地基的壓縮程度與固結(jié)程度出現(xiàn)差別，這樣就會出現(xiàn)新老路基的不均勻沉降，在新老路基相接處出就會出現(xiàn)高差、破損、裂縫等問題，所以研究新老路基拓寬后將發(fā)生的不均勻沉降問題具有十分重大的現(xiàn)實意義。 本文結(jié)合黑龍江省伊綏高速公路的應(yīng)用實踐，通過研究高速公路拓寬改建的案例，運用有限元軟件，本位對新老路路基拓寬過程中發(fā)生不均勻沉淀進行了數(shù)值分析，發(fā)現(xiàn)其中規(guī)律，針對此問題提出改進措施。 首先，對土體沉降變形涉及的基本理論進行介紹。分析地基應(yīng)力，應(yīng)力包括自重應(yīng)力和有效應(yīng)力，再依據(jù)疊加的原理，對產(chǎn)生在地基里任何位置處的附加應(yīng)力進行計算，推導了新路基的附加荷載。對比分析了不同的土本構(gòu)模型，對土的彈塑性性理論進行了介紹，研究有限元數(shù)值計算中土的本構(gòu)模型使用了Drucker-Prager模型。在此基礎(chǔ)上，，建立路基拓寬的有限元模型。對數(shù)值進行了計算，結(jié)果得出：新老路基之間的老路基受到了新路基所給的附加應(yīng)力而引起了不均勻的沉降變形；路基頂面的沉降由中心向兩側(cè)沿著路基橫斷面豎向呈勺型分布；如果拓寬寬度增加，所引起的新路基會使豎向沉降以及水平的位移明顯的增加；呈現(xiàn)線性增大的老路基頂面與拓寬寬度的水平位移，新路基頂面的水平位移的特點是先增大后減��；增加拓寬的寬度，新老路基間橫坡度的改變上總體是增加的，從增加的趨勢來說，是逐漸變小的；同一種拓寬寬度的情況與拓寬寬度變化是不同的，增加路基高度，新路基頂面水平位移最大值的變化是向著遠離老路基的方向；它的豎向沉降曲線會表現(xiàn)出劇烈的不均勻沉降運動，將慢慢的成為傾斜的直線形，與此同時會有一個沉降點出現(xiàn)在新老路基結(jié)合位置。 模擬挖開臺階的新老路基的結(jié)合部的數(shù)據(jù)表明，挖出一個臺階對不均勻沉降不會有很大的影響。在新路基底部鋪設(shè)土工格柵能夠?qū)⑿屡f路基之間的不均勻沉降作用在一定程度上減小，減小新路基的寬度，土工格柵的作用會變得更加明顯；輕質(zhì)路堤進行拓寬與普通路堤相比，前者可以有效的減小自重，使不均勻沉降有效的減小。分析結(jié)果表明：路堤彈性模量對不均勻沉淀的影響沒有路堤容重改變大，不均勻沉降問題可以通過使用容重小的輕質(zhì)路堤來解決。
[Abstract]:With the rapid and continuous development of the national economy, expressway construction has also entered the fast development of the fast lane, mileage is increasing, the quality is becoming more and more excellent;However, the traffic volume of expressway built in our country at the end of last century has become saturated, most of them are four-lane roads, and the road service is not as good as before, so it is imperative to widen and transform it.However, due to the difference of construction time between new and old subgrade and the deviation of subgrade's own characteristic, the compression degree and consolidation degree of foundation will be different after widening, and the uneven settlement of new and old roadbed will appear.There will be some problems such as height difference, breakage, crack and so on when the new and old roadbed meet each other, so it is of great practical significance to study the problem of uneven settlement after widening the new and old roadbed.Combined with the application practice of Yi-sui Expressway in Heilongjiang Province, by studying the case of expressway widening and rebuilding, using finite element software, this paper makes numerical analysis of uneven precipitation in the course of widening new and old roadbed.Find out the law, and put forward the improvement measures for this problem.Firstly, the basic theory of soil settlement and deformation is introduced.This paper analyzes the stress of the foundation, including the self-gravity stress and the effective stress. According to the principle of superposition, the additional stress produced at any position of the foundation is calculated, and the additional load of the new roadbed is deduced.Different soil constitutive models are compared and analyzed. The elastic-plastic theory of soil is introduced. The Drucker-Prager model is used to study the constitutive model of soil in finite element numerical calculation.On this basis, the finite element model of roadbed widening is established.The numerical value is calculated and the results show that the old road foundation between the new and old subgrade is subjected to the additional stress of the new roadbed and causes uneven settlement deformation.The settlement of the top surface of the subgrade is distributed vertically along the cross-section of the roadbed from the center to the two sides, and if the width of the roadbed is widened, the new roadbed will obviously increase the vertical settlement and the horizontal displacement.The horizontal displacement of the new roadbed's top surface increases first and then decreases, and when the width of the new roadbed is increased, the change of the transverse slope between the old and the new roadbed is increased.From the point of view of increasing trend, it is gradually becoming smaller, the situation of the same widening width is different from the change of widening width, the change of the maximum horizontal displacement of the new roadbed's top surface is toward the direction far away from the old roadbed by increasing the height of the roadbed.Its vertical settlement curve will show a violent uneven settlement motion, will slowly become a straight inclined shape, at the same time, there will be a settlement point in the new and old roadbed combination position.The data of the joint of the new and old roadbed with the excavated steps show that the excavation of a single step will not have a great effect on the uneven settlement.Laying geogrid at the bottom of the new road foundation can reduce the uneven settlement between the new and the old subgrade to a certain extent, reduce the width of the new roadbed, and the effect of the geogrid will become more obvious.Compared with ordinary embankment, lightweight embankment can effectively reduce the weight and reduce the uneven settlement.The results show that the influence of elastic modulus of embankment on uneven settlement is not as large as the bulk density of embankment, and the problem of uneven settlement can be solved by using light embankment with small bulk density.
【學位授予單位】：長安大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：U416.1

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