既有线附近基坑开挖对其路基变形的影响及支护效果的分析研究

发布时间：2018-01-07 02:42

本文关键词：既有线附近基坑开挖对其路基变形的影响及支护效果的分析研究　出处：《兰州交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：随着公路和铁路网的逐步完善,新建线路与既有线不可避免会形成交叉。在跨既有线桥梁施工中,基坑的开挖会导致既有路基发生变形和失稳,甚至影响行车安全。本文结合津秦铁路特大桥跨既有线铁路桥的施工,以桥墩承台基坑开挖为工程背景,依据Mohr-Coulomb屈服准则,采用FLAC3D软件作为计算工具建立了动、静载数值分析模型,探讨了基坑开挖的不同距离、角度、深度以及路基高度等参数对既有线的路基变形的影响,分析了基坑开挖中支护前后既有路基变形的影响规律。主要完成以下几方面工作： (1)通过查阅文献资料,了解基坑开挖引起周围构筑物变形的特点,对基坑开挖引起的主要变形以及地表沉降的计算方法进行综述。 (2)结合单线铁路路基模型,采用有限差分法进行数值分析,将列车荷载等效为静荷载分析在有无支护的情况下均质土层中基坑开挖参数变化对既有路基变形的影响,得到基坑施工中无支护情况下的临界开挖距离和临界开挖深度以及既有路基变形随开挖角度和路基高度的变化规律；并对不同开挖距离、开挖角度、开挖深度以及路基高度的支护效果进行分析。 (3)将列车荷载以激振力函数作用于上述模型,对既有路基进行基坑开挖的动态数值模拟,分析不同参数对支护后既有路基变形的影响。并将静态与动态模拟结果进行对比,结果表明：两种模拟方式下各参数对路基的变形影响规律基本一致,路基沉降主要由荷载的作用方式及范围决定,路基的水平位移与荷载的作用方式关系不大,主要受基坑开挖的影响。 (4)按照圆弧滑移面法基本原理,针对上述分析模型在不同开挖参数下基坑稳定性分析,得到支护前后各种工况下的基坑开挖时的稳定性系数,并对基坑稳定临界条件进行探索。
[Abstract]:With the gradual improvement of highway and railway network, new lines and existing lines will inevitably cross. In the construction of bridges with existing lines, excavation of foundation pit will lead to deformation and instability of existing subgrade. Even affect the safety of driving. Based on the foundation pit excavation of pier cap and Mohr-Coulomb yield criterion, this paper combined with the construction of the railway bridge over the existing railway line on the Jin-Qin railway, taking the excavation of the foundation pit of the pier cap as the engineering background. The dynamic and static load numerical analysis models are established by using FLAC3D software, and the influence of different distance, angle, depth and subgrade height of foundation pit excavation on the subgrade deformation of the existing railway is discussed. This paper analyzes the influence law of existing subgrade deformation before and after supporting in excavation of foundation pit, and mainly accomplishes the following work: 1) the characteristics of deformation of surrounding structures caused by excavation of foundation pit are understood, and the main deformation caused by excavation of foundation pit and the calculation methods of surface settlement are summarized. Combined with the single-track railway subgrade model, the finite difference method is used to carry out the numerical analysis. The train load is equivalent to static load to analyze the influence of excavation parameters of foundation pit in homogeneous soil layer on the deformation of existing subgrade under the condition of supporting or not. The variation law of the critical excavation distance, critical excavation depth and existing roadbed deformation with the excavation angle and the roadbed height in the case of no supporting in foundation pit construction is obtained. The support effect of different excavation distance, excavation angle, excavation depth and roadbed height is analyzed. 3) the dynamic numerical simulation of foundation pit excavation of existing roadbed is carried out by applying train load to the above model with exciting force function. This paper analyzes the influence of different parameters on the deformation of existing roadbed after supporting, and compares the static and dynamic simulation results. The results show that the influence of each parameter on the deformation of roadbed is basically the same under the two simulation modes. The settlement of subgrade is mainly determined by the mode and range of load, but the horizontal displacement of subgrade is not related to the mode of load, but is mainly affected by excavation of foundation pit. 4) according to the basic principle of circular slip surface method, the stability coefficient of foundation pit under various conditions before and after supporting is obtained according to the stability analysis of foundation pit under different excavation parameters according to the above analysis model. The critical condition of foundation pit stability is explored.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U445.55;U213.1

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