湿陷性黄土地基方形闭合地下连续墙桥梁基础承载性状模型试验研究

发布时间：2018-06-09 12:10

本文选题：闭合型地下连续墙 + 湿陷性黄土　；参考：《兰州交通大学》2016年硕士论文

【摘要】：随着国家西部大开发战略的实施,我国西部地区交通基础设施建设方兴未艾。西北地区广泛分布湿陷性黄土,在特殊的湿陷性黄土场地修建桥梁基础工程也具有特殊性,如地基湿陷变形对基础结构承载性质的影响等。相对于湿陷性黄土场地的桩基础、沉井基础及浅基础,本文探讨新型的闭合型地下连续墙桥梁深基础在湿陷性黄土地区的适应性。这种基础工程型式具有刚度大、适用范围广、工效高、承载稳定性好等优点。然而,在黄土地区采用闭合地下连续墙为桥梁深基础型式,一个不容忽视的问题便是湿陷性黄土遇水浸湿后易发生湿陷而引发的闭合墙负摩阻力问题。因此,研究湿陷性黄土地区黄土特性以及闭合型地下连续墙竖向承载性质及负摩阻力的变化规律具有重要的工程实际意义。本文通过研制湿陷性黄土的模型试验相似材料,将室内人工配制的湿陷性黄土材料应用于室内模型试验,制作室内闭合型地下连续墙模型开展试验工作,采用数值模拟方法对湿陷性黄土地区地下闭合墙的竖向承载性质以及负摩阻力发展规律进行了较为系统的研究。主要研究内容及研究成果如下:(1)在对黄土湿陷机理认识的基础上,选取砂、石英粉、膨润土、石膏、工业盐五种材料,经过大量配合比试验,可以得到不同湿陷系数的湿陷性黄土相似材料的配比。通过湿陷试验,得到该相似材料和天然湿陷性黄土具有相似的湿陷特征,浸水产生强烈的湿陷,可较好地运用于室内模型试验中。(2)通过室内模型试验研究湿陷性黄土地区闭合型地下连续墙桥梁基础的竖向承载能力和负摩阻力发挥性能,利用人工配制的湿陷性黄土相似材料作为模型土,表面进行处理后的有机玻璃作为模型墙体,制作25cm(长)×25cm(宽)×57cm(高)正方形闭合型地下连续墙模型。通过测试墙身轴力和墙内外壁侧摩阻力,土体湿陷附加应力和墙端阻力,以及土体湿陷变形量和桩顶沉降。分析湿陷性黄土地基闭合型地下连续墙的竖向承载性能、负摩阻力发挥特性。(3)闭合型地下连续墙竖向承载模型试验结果表明,墙外壁侧摩阻力的非线性分布现象明显,墙内壁下部侧摩阻力最大。墙外壁侧摩阻承担荷载最多,其次是墙内壁,墙端阻力及承台土反力承担荷载较少。(4)对于闭合型地下连续墙负摩阻力模型试验,周围土体浸水后,墙体承载力明显降低,外墙壁出现负摩阻力,呈“抛物线”状。同时内墙壁侧摩阻力、墙端阻力以及承台土反力较未浸水工况下得以进一步发挥。(5)运用有限元软件MIDAS/GTS,基于模量折减法对现场试验进行模拟。分析了荷载施加过程及土体湿陷过程中模型位移云图和应力云图的变化规律。通过对比现场试验工况以及室内模型试验工况,数值模拟结果所得到内外墙壁侧摩阻力,墙内壁侧摩阻力、墙身轴力等发展规律与室内模型试验以及现场试验结果趋势大体一致。本文的研究成果可以完善湿陷性黄土地区地下连续墙的研究理论,为工程设计和施工提供技术参考。
[Abstract]:With the implementation of the western development strategy of the country, the construction of traffic infrastructure in the western region of China is in the ascendant. The wet collapsible loess is widely distributed in the northwest area, and the construction of the bridge foundation project in the special collapsible loess site is also special, for example, the influence of the foundation wetting deformation on the bearing property of the foundation structure. The foundation of the site, the foundation of the caisson and the shallow foundation. This paper discusses the adaptability of the deep foundation of the new closed diaphragm wall bridge in the collapsible loess area. This type of foundation has the advantages of large stiffness, wide application, high work efficiency and good bearing stability. However, the closed diaphragm wall is used as the deep foundation of the bridge in the loess area. A problem that can not be ignored is the negative friction problem of the closed wall caused by collapsible collapsibility after wetting in wet loess. Therefore, it is of great practical significance to study the characteristics of the Loess in the collapsible loess area and the change rules of the vertical bearing property and negative friction of the closed diaphragm wall. The model test of collapsible loess is developed, and the indoor artificial wet collapsible loess materials are applied to the indoor model test, and the indoor closed diaphragm wall model is made to carry out the experimental work. The vertical bearing property and the negative friction resistance development law of the underground closed wall in the collapsible loess area are carried out by the numerical simulation method. The main research content and research results are as follows: (1) on the basis of the understanding of the mechanism of loess collapsibility, five kinds of materials such as sand, quartz powder, bentonite, gypsum and industrial salt are selected, and the ratio of collapsible loess similar materials with different collapsibility can be obtained by a large number of mix ratio tests. The similar material and natural collapsible loess have similar collapsibility characteristics, and the soaked water produces strong collapsibility. It can be well used in indoor model test. (2) through indoor model test, the vertical bearing energy and negative friction resistance of closed diaphragm wall bridge foundation in collapsible loess area are studied, and the artificial preparation is used. The collapsible loess similar material is used as model soil, and the processed organic glass is used as a model wall. The model of 25cm (long) x 25cm (wide) x (wide) x 57cm (high) square closed diaphragm wall is made. By testing the axial force of the wall and the friction resistance of the wall and inside the wall, the additional stress and wall end resistance of the soil, as well as the amount of soil collapsible deformation, and the amount of soil collapsible deformation are measured. The vertical bearing capacity of the closed diaphragm wall of collapsible loess foundation is analyzed. (3) the vertical bearing model test results of closed diaphragm wall show that the nonlinear distribution of the friction resistance on the outer wall of the wall is obvious, and the friction resistance of the lower side of the wall is the largest. The friction resistance of the outer wall of the wall is the most. Secondly, the inner wall of the wall, the wall end resistance and the bearing soil reaction bear less load. (4) for the model test of the negative friction resistance of the closed diaphragm wall, the wall bearing capacity of the surrounding soil is obviously reduced and the external wall wall appears negative friction, which is "parabola". At the same time, the side resistance of the inner wall, the resistance of the wall end and the soil counterforce of the bearing platform are not soaked. Under working conditions, it can be further developed. (5) using the finite element software MIDAS/GTS, the field test is simulated on the basis of modulus reduction method. The change law of the model displacement cloud and stress cloud chart in the process of loading and soil collapsibility is analyzed. The results of numerical simulation are obtained by comparing the working conditions of the field test and the experimental working conditions of the indoor model. The research results of this paper can improve the research theory of the diaphragm wall in the collapsible loess area, and provide technical reference for engineering design and construction.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U446

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