高速公路路基拓宽不均匀沉降数值分析

发布时间：2018-04-03 05:37

本文选题：不均匀沉降　切入点：路基拓宽　出处：《长安大学》2014年硕士论文

【摘要】：随着国民经济高速持续不断地发展，高速公路建设的也进入了快速发展的快车道，里程不断增多，质量也越来越优良；然而我国在上个世纪末所修建的高速公路到现在交通流量已经趋于饱和，大多都是四车道道路，道路服务也是大不如前，对其进行拓宽改造是势在必行。但是，在拓宽后因为新老路基施工时间的差异以及路基本身特性的偏差，使地基的压缩程度与固结程度出现差别，这样就会出现新老路基的不均匀沉降，在新老路基相接处出就会出现高差、破损、裂缝等问题，所以研究新老路基拓宽后将发生的不均匀沉降问题具有十分重大的现实意义。本文结合黑龙江省伊绥高速公路的应用实践，通过研究高速公路拓宽改建的案例，运用有限元软件，本位对新老路路基拓宽过程中发生不均匀沉淀进行了数值分析，发现其中规律，针对此问题提出改进措施。首先，对土体沉降变形涉及的基本理论进行介绍。分析地基应力，应力包括自重应力和有效应力，再依据叠加的原理，对产生在地基里任何位置处的附加应力进行计算，推导了新路基的附加荷载。对比分析了不同的土本构模型，对土的弹塑性性理论进行了介绍，研究有限元数值计算中土的本构模型使用了Drucker-Prager模型。在此基础上，，建立路基拓宽的有限元模型。对数值进行了计算，结果得出：新老路基之间的老路基受到了新路基所给的附加应力而引起了不均匀的沉降变形；路基顶面的沉降由中心向两侧沿着路基横断面竖向呈勺型分布；如果拓宽宽度增加，所引起的新路基会使竖向沉降以及水平的位移明显的增加；呈现线性增大的老路基顶面与拓宽宽度的水平位移，新路基顶面的水平位移的特点是先增大后减小；增加拓宽的宽度，新老路基间横坡度的改变上总体是增加的，从增加的趋势来说，是逐渐变小的；同一种拓宽宽度的情况与拓宽宽度变化是不同的，增加路基高度，新路基顶面水平位移最大值的变化是向着远离老路基的方向；它的竖向沉降曲线会表现出剧烈的不均匀沉降运动，将慢慢的成为倾斜的直线形，与此同时会有一个沉降点出现在新老路基结合位置。模拟挖开台阶的新老路基的结合部的数据表明，挖出一个台阶对不均匀沉降不会有很大的影响。在新路基底部铺设土工格栅能够将新旧路基之间的不均匀沉降作用在一定程度上减小，减小新路基的宽度，土工格栅的作用会变得更加明显；轻质路堤进行拓宽与普通路堤相比，前者可以有效的减小自重，使不均匀沉降有效的减小。分析结果表明：路堤弹性模量对不均匀沉淀的影响没有路堤容重改变大，不均匀沉降问题可以通过使用容重小的轻质路堤来解决。
[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.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U416.1

【参考文献】