车辆荷载作用下风积沙和砾类土低路堤工程特性研究

发布时间：2018-06-06 08:07

本文选题：低路堤 + 车辆荷载　；参考：《长安大学》2015年博士论文

【摘要】：低路堤填筑高度小、工程量和占用土地少,可节约宝贵的土地资源,且易与自然景观融为一体,对自然生态环境影响小,已成为我国公路建设发展的一个重要方向。但是由于对低路堤在车辆荷载作用下的工程特性缺乏了解,在设计过程中参数选取不尽合理,导致路基发生较大沉降和路面开裂,降低了道路的服务水平,因此明确低路堤在车辆荷载作用下的工程特性对指导低路堤的设计与施工具有重要的理论意义和工程实用价值。本文依托交通运输部西部交通建设科技项目“新疆绿洲、荒漠地区干线公路路基合理高度研究”,采用室内试验、模型试验、数值模拟和理论分析等方法对低路堤在车辆荷载作用下的工程特性进行了系统地研究,主要研究内容及成果如下:1.采用四分之一车辆模型,考虑轮胎阻尼和路面不平度的影响以及车辆荷载的循环特征,得到了车辆附加动荷载和车辆动荷载的表达式。2.进行了动三轴试验,系统研究了新疆风积沙和砾类土的动应力-动应变关系、动弹性模量、阻尼比、临界动应力和动强度,总结了围压、含水率、压实度、动荷载作用频率以及初始静偏应力对风积沙和砾类土的动应力-动应变关系、动弹性模量、阻尼比的影响规律,提出了动应力-动应变关系双曲线模型、动弹性模量-应变关系幂函数模型和动强度-作用次数关系指数曲线模型,确定了不同条件时风积沙和砾类土的临界动应力。3.开展了3种地基状态时砾类土低路堤和风积沙低路堤模型试验,通过改变加载大小和频率模拟不同轴重和不同行驶速度的车辆荷载,研究了低路堤在静载、短时动载和长时动载作用下的工程特性,得到了路基和地基范围内各深度处的应力、各结构层的应变以及应力的传递衰减特性。明确了静载大小、动荷载峰值、动荷载作用频率、动荷载作用次数、地基含水率和路基填料对低路堤工程特性的影响规律,分析了低路堤在静载、短时动载和长时动载作用下工程特性的差异,提出了长时动载作用下低路堤动应力累积模型。4.建立了车-路三维动力分析有限元模型,通过现场实测数据和模型试验结果验证了模型的正确性,基于该模型分析了路堤高度和模量、基层厚度和模量、面层厚度和模量、车辆移动速度、超载率和路面不平度等因素对车辆荷载作用下低路堤不同深度处动应力和路基工作区的影响。5.基于层状结构下静载的传递和扩散公式,依据低路堤模型试验和数值模拟分析结果,考虑车辆荷载行驶速度、路面不平度、超载、累积效应以、道路结构和应力衰减的影响,推导了低路堤动应力的计算公式。应用该公式给出了新疆低路堤地基换填加固参数的取值。
[Abstract]:The low embankment construction height is small, the engineering quantity and the occupation land is little, can save the precious land resources, and is easy to merge with the natural landscape, the influence to the natural ecological environment is small, has already become an important direction of the highway construction development of our country. However, due to the lack of understanding of the engineering characteristics of the low embankment under vehicle load, and the unreasonable selection of parameters in the design process, the subgrade has a large settlement and pavement cracking, which reduces the service level of the road. Therefore, it is of great theoretical significance and practical value to clarify the engineering characteristics of low embankment under vehicle load for guiding the design and construction of low embankment. This paper relies on the scientific and technological project of western traffic construction of Ministry of Communications and Transport, "study on reasonable height of highway roadbed in oasis and desert area of Xinjiang", adopts indoor test and model test, The engineering characteristics of low embankment under vehicle load are systematically studied by numerical simulation and theoretical analysis. The main contents and results are as follows: 1. Based on the model of 1/4 vehicle, considering the influence of tire damping and road roughness, and the cyclic characteristics of vehicle load, the expressions of additional dynamic load and dynamic load of vehicle are obtained. Dynamic triaxial tests were carried out. The dynamic stress-strain relationship, dynamic elastic modulus, damping ratio, critical dynamic stress and dynamic strength of aeolian sand and gravel soil in Xinjiang were systematically studied, and the confining pressure, moisture content, compaction degree were summarized. A hyperbolic model of dynamic stress-strain relation, dynamic modulus of elasticity and damping ratio is proposed, which is influenced by the frequency of dynamic load and the initial static deflection stress on the dynamic stress-strain relationship of aeolian sand and gravel soil. The power function model of dynamic elastic modulus-strain relationship and the exponential curve model of dynamic intensity-action times are used to determine the critical dynamic stress of aeolian sand and gravel soil under different conditions. The model tests of low gravel embankment and eolian sand low embankment under three kinds of foundation conditions were carried out. The static load of low embankment was studied by changing the loading size and frequency to simulate the vehicle loads with different axle loads and different driving speeds. Under the action of short-time dynamic load and long-time dynamic load, the stress at each depth, the strain of each structural layer and the transmission and attenuation characteristics of stress in the subgrade and foundation are obtained under the action of short-time dynamic load and long-time dynamic load. The influence of static load, peak dynamic load, frequency of dynamic load, moisture content of foundation and filling of subgrade on the engineering characteristics of low embankment are defined. The static load of low embankment is analyzed. The dynamic stress accumulation model of low embankment under the action of long time dynamic load and short time dynamic load is proposed. The finite element model of three-dimensional dynamic analysis of vehicle-road is established, and the correctness of the model is verified by the field measured data and model test results. Based on the model, the height and modulus of embankment, the thickness and modulus of base course, the thickness and modulus of surface layer are analyzed. The effect of moving speed, overload rate and road roughness on dynamic stress at different depths of low embankment and subgrade working area under vehicle load. Based on the formula of static load transfer and diffusion under layered structure, according to the results of model test and numerical simulation analysis of low embankment, the effects of vehicle load speed, road roughness, overload, cumulative effect on road structure and stress attenuation are considered. The formula for calculating dynamic stress of low embankment is derived. The formula is used to give the values of the parameters for the replacement and reinforcement of the foundation of Xinjiang low embankment.
【学位授予单位】：长安大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U416.1

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