【作者】 孙岩；

【导师】 黄立葵；

【作者基本信息】 湖南大学 ， 交通运输工程， 2011， 硕士

【摘要】 研究人员通过试验和宏观有限元分析认为开级配沥青碎石能够防止反射裂缝,却很少有人能从细观层面上做出解释。本文建立了开级配沥青碎石随机集料数值模型,并以此为基础,利用离散元理论分析了开级配沥青碎石防止反射裂缝的细观机理,以期道路工作者对该机理有更好的理解。本文利用离散元程序生成了开级配沥青碎石(嵌挤状态)二维圆形随机集料模型,并根据开级配沥青碎石弹性模量和抗压强度,通过数值单轴试验拟合模型细观参数。本文用投放颗粒的思想更深入研究了建立松散圆形随机集料模型的具体方法,要求各个颗粒不互相重叠,并在圆形集料模型基础上通过延“凸”生成了凸多边形随机集料模型,以期对更深入地研究沥青混合料有帮助。为将细观试件同宏观路面结构联系起来,本文利用位移法的思想,在宏观路面结构中划出一个方形细观试件,并保证细观试件与路面结构其他部分完全连续,利用有限元方法计算其在最不利荷载作用下的变形结果,并以此作为细观分析的加载条件。基于不连续体系的离散元理论可以很好地分析开级配沥青碎石结构。对模型赋予细观参数、施加边界位移条件,经离散元法分析后,本文认为是开级配沥青碎石的大孔隙允许集料有更多的空间协调变形,从而防止裂缝的扩展。使用离散元法从细观层面分析沥青混合料是一种较新的方法,相信会有很大发展空间,便于研究人员更好地理解沥青混合料。更多还原

【Abstract】 By tests and finite element analysis for the macro-structure of pavements, researchers found that the open-graded asphalt macadam can prevent the reflection crack in asphalt pavements, but very few people can explain it on meso-level. A random aggregate structure model for the open-graded asphalt macadam was established in this thesis, based on this model, then the meso-mechanism that the open-graded asphalt macadam can prevent reflection crack was analyzed by DEM (Discrete Element Method) to help the researchers understand this problem better.A circular random aggregate structure model in squeezed state was established by DEM, the meso-parameter of the model for DEM was fitted from the elastic modulus and compressive strength of the open-graded asphalt macadam by numerical uniaxial test. The specific method how to establishes loose circular random aggregate structure model was deeply studied in this thesis by throwing particles into the model, particles in the model should not overlap each other, random convex polygon aggregate structure model could be produced by the process of extension to convex polygon based on the circular model, it may be helpful for deep research on asphalt concrete.To establish the relationship between the meso-model and the entire pavement structure, the idea of displacement method was used, a rectangle in the pavement structure model was taken as the meso-model, and it should be ensured to be completely continuous with other parts of the pavement structure model, then the deformation results of the meso-model in the worst loading conditions was calculated by the finite element analysis of the entire pavement structure, it was used to be the load conditions for meso-analysis.DEM which is based on the discrete system can be well used to analyze the open-graded asphalt macadam structure. The discrete element analysis after the assignment of meso-parameters and loads to the model shows that the greater porosity of the open-graded asphalt macadam allows aggregates more space to coordinate to prevent extension of the crack.It is a relatively new method to analyze the asphalt mixture by DEM on meso-level. It is believed to have a great development to help researchers better understand the asphalt mixtures.更多还原