基于土基耐久性的路基与半刚性基层间的过渡层研究

发布时间：2018-12-26 16:53

【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。
[Abstract]:The subgrade is the foundation of the pavement structure, but during the long-term operation, the durability of the subgrade soil can change due to the influence of the external water and the load. The main performance is the attenuation of the strength, thus causing the damage of the pavement structure. The transitional layer is set between the subgrade and the semi-rigid base layer, and the effect of the roadbed disease on the pavement structure can be effectively relieved, but the design method of the system is not currently designed for the thickness and the material of the transition layer. Therefore, from the study of the durability of the subgrade soil and its influence on the pavement structure, the paper studies the design method of the transition layer between the subgrade and the semi-rigid base layer based on the action mechanism of the transition layer. Water is the main factor that affects the durability of the subgrade soil, and the fine-grained soil has strong water-holding capacity, and its properties are more susceptible to water. In this paper, the effects of soil quality on the law of water migration and the durability of different types of soil are compared. The main shape of the road surface disease caused by the change of the durability of the subgrade soil is summarized, and the road surface diseases induced by the high water content of the subgrade under different traffic conditions are investigated. formula; the final combined road is used for quantitatively analyzing the attenuation amplitude of the fatigue life of the pavement structure caused by the insufficient durability of the subgrade, and the calculation result is compared with the actual situation; The resilience modulus of the subgrade soil is an important parameter of the pavement structure design, and is the main part of the durability of the subgrade soil. In this paper, the stress-dependence and water-sensitivity of the subgrade soil are analyzed firstly, and the stress-dependent and water-sensitive coupling model of the resilience modulus of the subgrade soil is set up according to the soil water characteristic curve, and the stress-dependent and water-sensitive coupling model of the subgrade soil resilience modulus is established. Line verification; secondly, according to the external load in the actual environment and the change of water in the subgrade, the change trend of the rebound modulus of the subgrade soil during operation is analyzed; and finally, the traffic volume of the 鈥渄ynamic鈥，

本文编号：2392409