基于分段变维的沥青路表纹理磨光行为分析

Polishing Behavior Analysis of Asphalt Pavement Surface Texture Based on Piecewise Variable Dimension Fractal

为了多尺度表征沥青路表纹理磨光行为,揭示其表面纹理磨光演化机理,首先基于沥青表面纹理的自仿相似特性,引入高差自相关函数,将常维分形扩展至分段变维分形,建立了表面纹理分段变维评价模型。其次,分别选取高磨光值的玄武岩和低磨光值的石灰岩成型沥青混合料试件,对其进行岩相鉴定,借助平板磨光机进行室内加速磨光试验,测量了不同磨光状态下的动摩擦因数,同时采用三维激光扫描仪获取了表面纹理信息。最后分析了断面轮廓分段变维高差自相关特性,并与摩擦因数进行了对比分析。结果表明:路面在大尺度范围内有明显的分段变维特征,高差自相关函数可以多尺度量化沥青混合料表面微观至宏观纹理特征,2种路表宏微观纹理界限波长为0.4 mm左右;截止波长可以作为评价普通磨光和差异磨光的指标,其中水平截止波长表示路面平均微凸体尺寸,垂直截止波长表示骨料平均高度;随着磨光转数的增加,受2种磨光机制影响的试件(玄武岩)表面纹理的水平截止波长变化甚微,而受普通磨光机制作用的试件(石灰岩)表面纹理的水平与垂直截止波长均下降明显;在道路设计和施工过程中,选取矿物组成成分更多、粒径分布更广、矿物质间硬度相差较大的集料,更容易受到2种磨光机制的影响,从而有助于沥青路表保持足够的表面纹理水平,延缓路面抗滑性能衰减速率。

An attempt was made to characterize the polishing behavior of the asphalt pavement surface texture and to reveal the evolution mechanism of the surface texture in the polishing process.First,the height difference correlation function was introduced by extending the single dimensional fractal to the piecewise variable dimension fractal based on self-affinity of the surface texture,and the piecewise variable dimension fractal evaluation model of the surface texture was established.Second,basalt and limestone,having,high and low polished stone value,were respectively selected to mold the asphalt mixture,the indoor accelerated polishing test was conducted by the plate-polishing machine,and the dynamic friction coefficient in different polishing cycles was measured.Finally,the height difference correlation characteristic of the profile was analyzed and compared with the friction coefficient.Research results indicate that asphalt pavement surface has obvious piecewise variable dimension fractal characteristics,the height difference correlation function can quantify the microtexture and macrotexture characteristics of the asphalt mixture surface,and the boundary wavelength between the microtexture and macrotexture is approximately 0.4 mm.The cut-off wavelength can be the indexes to distinguish general polishing and differential polishing.The horizontal cut-off wavelength corresponds to the largest asperity,and the vertical cut-off wavelength indicates the mean height of the aggregate.With an increase in the number of polishing cycles,the horizontal cut-off wavelength of the basalt specimen which affected by the two polishing mechanisms changed little,whereas both horizontal and vertical cut-off wavelengths decreased significantly for the limestone specimen,which was only affected by the general polishing.In the design and construction process,the aggregates that had a greater mineral composition,wider particle size distribution,and a greater difference in hardness are more easily affected by the two polishing mechanisms so as to keep enough asphalt surface texture and delay the skid resistance performance attenuation rate.