【作者】 弋晓明；

【导师】 顾金才； 李术才； 王松根；

【作者基本信息】 山东大学 ， 岩土工程， 2014， 博士

【摘要】 路基是路面结构的基础,但在长期的运营过程中,受外界水分、荷载等因素的影响,路基土的耐久性会发生变化,主要表现为强度的衰减,从而引起路面结构的破坏。在路基与半刚性基层间设置过渡层,可有效缓解路基病害对路面结构的影响,但目前尚没有系统的设计方法针对过渡层的厚度、材料等进行专门的设计。因此,本文从研究路基土的耐久性特征及其对路面结构的影响出发,基于过渡层的作用机理,对路基与半刚性基层间的过渡层的设计方法进行研究。水分是影响路基土耐久性的主要因素,而细粒土具有较强的持水能力,其性质更易受水分的影响。论文首先通过室内试验模拟粉土和粘土内部水分的渗透作用和毛细上升作用,在此基础上,对比分析土质对水分迁移规律的影响,以及不同类型土的耐久性变化特征；其次针对在不同交通量情况下路基含水率较高而诱发的路面病害进行调查,总结出路基土耐久性变化引起的路面病害的主要形式；最后结合路用环境定量分析路基耐久性不足引起的路面结构疲劳寿命的衰减幅度,计算结果与实际情况相符。路基土的回弹模量是路面结构设计的重要参数,也是反映路基土耐久性的主要指标。论文首先分析路基土的应力依赖性和水敏感性,并根据土水特征曲线,以基质吸力为媒介,建立路基土回弹模量的应力依赖性和水敏感性耦合模型,且通过室内试验进行验证;其次结合实际环境中外部荷载和路基内部水分的变化,分析运营期间路基土回弹模量的变化趋势；最后将“动态”的交通量与“静态”的轴载进行相互转化,提出我国半刚性基层沥青路面典型结构在不同交通量等级下的容许最小路基强度。弹性层状体系理论是我国路面结构设计的基础理论。论文首先结合弹性层状体系的力学响应特征,研究厚度、模量等结构参数变化对各结构层受力的影响,分析影响弹性层状体系内部各结构层受力的直接因素,从理论上提出设置过渡层可以有效改善路基强度衰减对路面结构的影响；其次研究过渡层的作用机理,主要包括对下层结构的补强作用和对上层荷载的削弱作用,并分析过渡层的厚度、模量等结构参数对其作用的影响；最后依据补强作用原理,建立补强后当量模量的预估模型,并提出基于补强递增系数的的最佳补强理论和经济模量,既能满足结构的力学性能要求,又能充分利用过渡层的强度。级配碎石既有一定的强度又能适应一定的变形,是作为过渡层的理想材料,合理的级配是保证级配碎石过渡层的路用性能的重要前提。论文首先对目前常用的级配设计方法进行分析,其本质是分形理论的不同应用形式,并提出集料的分形特征；然后对目前各国规范中级配碎石的分形特征进行分析,依据固体体积率、CBR、二次松散系数等路用性能等进行优化,提出适用于过渡层的级配碎石的级配范围,并与我国规范中规定的级配范围进行性能对比,检验级配碎石分形级配范围的合理性。论文结合高含水率粉土路基路段的公路大修工程,对级配碎石过渡层的设计及应用进行说明。首先,对路面病害类型及主要成因进行详细分析,认为路基土耐久性衰减是引起路面损坏的主要原因,符合过渡层的设置条件；其次,结合现场交通量条件利用最佳补强理论对级配碎石过渡层的厚度和模量进行设计,并能够满足结构验算的要求；最后,总结出级配碎石的施工工艺及质量检验标准。更多还原

【Abstract】 Subgrade plays a supporting role to the pavement structure, while the property of subgrade soil changes as the effect of water and bad along the running. And the strength attenuation appears easily, which would result in the damage of pavement. The transition layer between subgrade and semi-rigid base could decrease the influence of subgrade defect on pavement structure. But now there is no systematic design method to guide the design of transition layer. So the durability of subgrade soil and its impact is studied, and then the design method of transition layer is proposed basing on the function of transition layer.Water has an important influence on the property of subgrade soil, and the fine-grained soil retains water strongly, so its property is easier to be impacted by water. First, the permeation and capillarity of silt and clay are simulated through laboratory test, and then the influence of soil group on the water migration and the durability are analysed. Second, the disease of pavement caused by subgrade with high water content is summarized by means of field survey. At last, the quantitative analysis of the fatigue life of pavement structure is proceeded combined with the application environment.Resilient modulus of subgrade soil is an important parameter in pavement structure design, which reflects the durability of subgrade soil. First, the stress-dependent and water sensitivity of soil are analysed separately, and then the coupling model is built by using matric suction. Second, the variation tendency of resilient modulus is researched based on the change of water conten and vehicle load. At last, the division method fot the grade of traffic volume is converted from vehicle number to axle load, and then the allowable minimum strength of subgrade for the typical asphalt pavement structure with semi-rigid base is suggested under different level of traffic volume.The elastic layer system theory is the basic for the design of pavement structure. First, the influence of thickness and modulus on the mechanics characteristic of the layered structure is researched, then the immediate influence factor is found out, thereafter the idea that the transit ion layer could minis h the influence of subgrade strength attenuation on pavement structure effectively is come up. Second, the function of transition layer is researched in terms of mechanical mechanism, which contains reinforcing the understructure and weakening the load, and then the influence of structure parameters such as thickness, modulus on the function is studied. Finally, basing on the reinforcement, the prediction model on equivalent modulus is established, after that the optimum reinforcement theory and the best modulus are put forward, which can meet the structure stress and make use of the strength of transition layer fully.Graded aggregate has enough strength and can moderate deformation. It’s a good material to construct transition layer, and the perfect graduation is important to the performance of the structure. First, different grading design methods are discussed, and it’s found that all these methods are different forms of fractal theory, also the fractal feature of aggregate is presented. Second, fractal features of aggregate in specification of different country are analysed, and then the scope of gradation is optimized by the solid volume rate, CBR and secondary coefficient of volumetric expansion. At last, the rationality of the suggested gradation range is examined by laboratory tests.The transition layer is applied in the maintenance works of a highway. First, the disease is examined, and it’s showed that the strength attenuation of subgrade is the key factor to destroy the pavement structure, so the transition layer is suitable to use in the engineering. Second, the optimum reinforcement theory is used to design the transition layer basing on the traffic volume, and the result achieves the structure checking. At last, the construction technology and quality inspection standards of graded aggregate are summarized.更多还原