考虑非均布荷载及动态模量特性的沥青路面结构厚度设计应用研究

发布时间：2019-01-30 21:25

【摘要】：半刚性基层沥青路面在我国路面结构形式中应用最为广泛。然而，由于各种原因，半刚性基层沥青路面的使用寿命往往不够理想，尤其在我国。据有关资料统计，与发达国家半刚性基层沥青路面的使用寿命相比，我国的使用年限较短，往往是3~5年，有的甚至通车不到1年就会出现严重的损坏。这其中既有施工的原因、材料选择与设计方面的原因，也有结构厚度设计的原因。实际上，根据我国沥青路面结构设计规范，由于半刚性基层的强度高、变形小，，半刚性基层沥青路面所计算出来的层底往往是受压，而不是受拉，导致弯拉应力或拉应变的设计控制指标就起不到防止相应结构层疲劳开裂的作用；同样，由于半刚性基层的强度高，弯沉指标对结构层的厚度设计，尤其是沥青层的厚度，也起不到控制作用。造成这种问题的因素也有很多，其中重要的一点，就是结构厚度设计用的轮胎-路面接地压力和结构层模量的取值不够准确。目前常用的力学-经验路面结构设计方法，轮载对路面的作用都认为是圆形均布荷载。然而，即使是同一路面同一车辆荷载，其轮载的作用力大小和作用形式都是不同的，进而产生的路面力学响应也不同。同时，荷载的作用力大小分布受车辆负荷、轮胎胎压及胎面花纹等因素的影响而呈现很大的不同，远非均匀性所能描述。由车辆荷载引起的路面结构内的应力脉冲波形，也并非简单的正弦波状，而是随着路面深度的增加，波形从矩形逐渐向半正弦波变换，当沥青层较厚时，更接近钟罩型。另一方面，我国规范规定沥青路面沥青层的模量取值采用静态模量，但静态模量显然太过简单，基本上不能反映沥青混合料的特性。美国AASHTO建议采用动态模量，是因为动态模量能很好的体现沥青路面实际的动态受力情况，但由于在进行动态模量试验时仅仅考虑了半正弦波加载，无法全面反映其实际的受力情况。因此，在美国AASHTO研究的基础上，有必要对动态模量做进一步的研究。本文从路面结构厚度设计的两个主要参数（车辆荷载和动态模量）入手，进行沥青路面结构设计的优化研究。首先，考虑试验温度、加载波形及加载频率等因素对动静态模量的影响，利用加载波形的研究成果对动态模量试验荷载的控制程序进行二次开发，并应用到试验中。第二，通过试验结果，对各沥青层的动静态模量取值进行研究，并确定模量值。第三，利用ANSYS和BISAR软件对路面结构力学响应进行分析，建立可靠的ANSYS有限元模型，再利用建立的有限元模型，对同一结构不同模量组合下的路面结构进行力学分析，并了解其差异性。最后，根据沥青路面厚度设计的控制指标，确定不同模量组合下的沥青路面厚度。
[Abstract]:Semi-rigid base asphalt pavement is widely used in pavement structure in China. However, due to various reasons, the service life of semi-rigid asphalt pavement is often not ideal, especially in China. According to the statistics, compared with the service life of semi-rigid base asphalt pavement in developed countries, the service life of our country is shorter, often is 3 ~ 5 years, some even opened to traffic for less than one year will appear serious damage. There are not only the reasons of construction, material selection and design, but also the reasons of structural thickness design. In fact, according to the code for structural design of asphalt pavement in China, due to the high strength and small deformation of semi-rigid base, the base of asphalt with semi-rigid base is often under pressure rather than tension. The design control index which leads to the bending tension stress or tension strain can not prevent the fatigue cracking of the corresponding structural layer. Similarly, because of the high strength of semi-rigid base, the deflection index can not control the thickness design of structural layer, especially the thickness of asphalt layer. There are many factors that cause this problem. One of the important factors is that the earthing pressure and the modulus of the structure layer used in the design of the thickness of the structure are not accurate enough. At present, the mechanical-empirical pavement structure design method, the role of wheel load on the pavement is considered to be circular uniform load. However, even if the same vehicle load on the same road surface, the force and form of the wheel load are different, and the mechanical response of the pavement is also different. At the same time, the force distribution of load is influenced by vehicle load, tire pressure and tread pattern, which is far from uniform. The stress pulse waveform in pavement structure caused by vehicle load is not a simple sine wave, but with the increase of pavement depth, the waveform gradually changes from rectangle to semi-sine wave, and when the asphalt layer is thicker, it is closer to the bell cover type. On the other hand, the standard of our country prescribes that the modulus of asphalt pavement is static modulus, but the static modulus is too simple to reflect the characteristics of asphalt mixture. Dynamic modulus is recommended by AASHTO because it can well reflect the actual dynamic loading of asphalt pavement, but the semi-sinusoidal loading is only considered in the dynamic modulus test. Can not fully reflect its actual force situation. Therefore, it is necessary to do further research on dynamic modulus on the basis of AASHTO research in the United States. This paper starts with two main parameters (vehicle load and dynamic modulus) of pavement structure thickness design, and carries on the optimization research of asphalt pavement structure design. Firstly, considering the influence of test temperature, loading waveform and loading frequency on dynamic and static modulus, the control program of dynamic modulus test load is developed by using the research results of loading waveform, and applied to the test. Secondly, through the test results, the dynamic and static modulus of each asphalt layer is studied, and the modulus value is determined. Thirdly, the mechanical response of pavement structure is analyzed by using ANSYS and BISAR software, and a reliable finite element model of ANSYS is established. Then, the mechanical analysis of pavement structure with different moduli of the same structure is carried out by using the established finite element model. And understand its difference. Finally, according to the control index of asphalt pavement thickness design, the asphalt pavement thickness under different modulus combination is determined.
【学位授予单位】：武汉工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U416.217

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