摘 要

近十年来，我国经济总量翻了几番，货物流通和人员流动越来越频繁，而现阶段我国交通运输能力有限，并不能满足经济发展的需要。为了解决目前交通运输能力与交通需求之间的矛盾，单靠新建交通线路是不够的，因为新建线路周期较长，成本较高，而既有线路基帮宽工程不仅能提高旧路的交通运输能力，缓解交通运输压力，而且建设周期较短、成本较低。所以既有线路基帮宽是缓解当前交通运输供需不平衡问题的切实可行的办法。

在既有线路基帮宽施工过程中,新旧路基之间的结合部位会产生不均匀沉降，这是既有线路基帮宽面临的最大难题。本论文主要研究工作为:基于弹塑性的本构模型，确定所需要的单元类型，建立相应的几何模型，选择合适的材料参数，选择五种台阶开挖方案，运用有限单元法对既有线路基帮宽施工过程进行数值模拟，得到台阶开挖后旧路基的变形色彩分布云图和新路堤水平分层填筑后新旧路基整体的变形色彩分布云图，根据数值模拟所得到旧路基和新旧路基整体的变形色彩分布云图，分析台阶开挖卸载和新路堤分层填筑加载对旧路基和新旧路基整体变形特性的影响规律，进而研究路堤加宽方式、路堤高度、新帮宽路堤性能等对路基变形特性的影响规律。

根据数值模拟的结果及结果分析，总结既有线帮宽路基的破坏模式和破坏机理，总结新旧路基之间产生不均匀沉降的各方面原因，对既有线路基帮宽的施工方案提出相应的优化措施，给出一些具有一定参考价值的意见。

关键词：新旧路基；既有线路基帮宽；不均匀沉降；有限元法；变形特性

Abstract

Over the past decade, China's total economic volume has doubled, the flow of goods and personnel are more and more frequent, But at this stage, China's transportation capacity is limited, and can not meet the needs of economic development. In order to solve the current contradiction between traffic capacity and traffic demand, it is not enough to build a new traffic route only. Because a new route has a long cycle and a high cost, Expansion of existing roadbeds can not only improve the transportation capacity of the old road, to ease the transport pressure, but also has the shorter construction period and the lower cost. So expansion of existing roadbeds is a practical way to help ease the current transport supply and demand imbalance.

In this paper, the main research work is as follows: based on the elasto-plasticity constitutive model, the unit type is defined, the corresponding geometric model is established , the appropriate material parameters are selected, the five step excavation schemes are chosen, and the finite element method is used to simulate the construction process of expansion of existing roadbeds. The deformation distribution color maps of the old roadbed after the step excavation and the overall roadbed after the new roadbed integration filling up are obtained. According to deformation distribution color map of the old roadbed and the overall roadbed from the numerical simulation, the influence of step excavation unloading and new embankment filling up loading on the overall roadbed to deformation characteristics of old subgrade and the overall subgrade are analyzed. Then the influence of embankment widening method, the embankment height and the new embankment performance to deformation characteristics of roadbed are studied.

According to the results of numerical simulation and the results of the analysis, the failure modes and failure mechanism of the subgrade after being widen are analyzed, the causes of uneven settlement between the old and new subgrade is summarized.Finally the corresponding optimization measures for the construction scheme of expansion of existing roadbeds are put forward and some ideas with a certain reference value are given.

Keywords:the new and old subgrade; expansion of existing roadbeds; uneven settlement; finite element method; deformation characteristics

目 录

第1章 绪论.........................................................1

1.1 选题的背景及意义..............................................1

1.2 国内外在既有线路基帮宽方面的研究现状..........................1

1.2.1 国外在既有线路基帮宽方面的研究现状.........................1

1.2.2 国内在既有线路基帮宽方面的研究现状.........................2

1.3 既有线路基帮宽施工方式及其特点................................2

1.4 既有线路基帮宽施工的工程措施..................................3

1.5 论文研究的内容................................................5

第2章 非线性弹塑性有限元分析的基本理论.............................6

2.1 有限单元法的发展..............................................6

2.2 有限单元法的步骤..............................................6

2.3 土体的本构模型................................................6

2.3.1 土体的非线性特性...........................................7

2.3.2 土体的塑性特征.............................................7

2.3.3 土体的本构模型.............................................7

2.4 本章小结......................................................8

第3章 既有线帮宽路基性状特征......................................9

3.1 工程地质......................................................9

3.2 工程措施......................................................9

3.3 本章小结.....................................................11

第4章 既有线路基帮宽的弹塑性有限元分析............................12

4.1 弹塑性有限元分析的基本假定...................................12

4.2 单元类型的选择...............................................12

4.2.1 平面应变单元..............................................12

4.2.2 土工格栅单元..............................................13

4.3 几何模型的建立和计算参数的确定...............................13

4.3.1 几何模型的建立............................................13

4.3.2 计算参数的确定............................................13

4.4 旧路基初始地应力场的确定与施加...............................14

4.5 既有线路基帮宽施工过程的模拟.................................14

4.6 新旧路基在新帮宽路基分级荷载作用下变形性状...................15

4.6.1 既有线路基帮宽方式对变形的影响............................15

4.6.2 路堤高度对变形的影响......................................16

4.6.3 填筑材料的弹性模量对变形的影响............................17

4.6.4 填筑材料的密度对变形的影响................................17

4.6.5 旧路堤不同削坡和台阶开挖方案对变形的影响..................17

4.7 本章小结.....................................................22

第5章 既有线路基帮宽施工方案优化..................................23

5.1 既有线路基帮宽工程的主要破坏形式.............................23

5.2 帮宽路堤的破坏模式...........................................23

5.3 帮宽路堤破坏机理分析.........................................25

5.3.1 新旧路基变形不协调........................................25