考虑砂浆随机分布的多孔沥青混合料黏附/黏聚失效行为

Adhesion/cohesion failure behavior of porous asphalt concrete considering mortar random distribution

为获得更加真实的多孔沥青混合料(PAC)黏附/黏聚失效行为,提出了一种考虑砂浆随机分布的细观有限元建模方法;基于X射线CT扫描和图像处理技术量化了PAC的真实细观结构和砂浆分布,研究了砂浆的随机分布特性;通过可精确控制砂浆厚度的拉拔试验评价了不同厚度砂浆的黏附/黏聚性能,确定了不同厚度砂浆对应的内聚力模型参数;在砂浆-集料边界和砂浆内部嵌入零厚度内聚力单元,并基于PAC内不同区域的砂浆厚度赋予该区域内聚力单元相应的模型参数,最终构建了考虑砂浆随机分布的细观有限元模型(模型A),研究了PAC黏附/黏聚失效行为的细观演化过程。研究结果表明:推荐将试件分割为36份用于表征砂浆的随机分布特性,砂浆厚度对其黏附/黏聚性能、失效模式以及内聚力模型参数具有显著影响,当砂浆厚度小于0.9 mm或在1.2~1.8 mm时为黏附失效,大于1.9 mm时为黏附-黏聚混合失效,其他厚度下为黏聚失效,且同一失效模式下,黏附/黏聚强度随着砂浆厚度的增大而增大;与不考虑砂浆随机分布的细观有限元模型(模型B)相比,模型A和B的起裂点均为黏附失效,但失效位置不同,模型B以单一的黏附失效为主,模型A表现出多种黏附/黏聚失效行为,与现场复杂的黏附/黏聚失效行为更加一致;砂浆的随机分布对PAC黏附/黏聚失效过程、应力分布、裂缝发展具有显著的影响,故考虑砂浆的随机分布能够更加准确地识别PAC黏附/黏聚失效的最不利位置,增大砂浆厚度能够延缓黏附/黏聚失效的扩展过程。

A meso-scale finite element modeling method for incorporating the random distribution of mortar was proposed to obtain a more realistic adhesion/cohesion failure behavior of porous asphalt concrete(PAC).The actual meso-structure and mortar distribution of PAC were quantified by using X-ray CT scanning and image processing technology,and the random distribution characteristics of mortar were evaluated.The adhesion/cohesion properties of mortars with different thicknesses were evaluated by pull-off test that can accurately control the thickness of mortar,and the cohesive zone model parameters corresponding to different thicknesses of mortar were determined.Zero-thickness cohesive elements were embedded at the mortar-aggregate interface and within the mortar,and corresponding model parameters were assigned to the cohesive elements based on the mortar thicknesses in different regions of PAC.Finally,a meso-scale finite element model considering mortar random distribution(Model A) was built to study the meso-scale evolution process of PAC adhesion/cohesion failure behaviors.Research results indicate that it is recommended to divide the specimens into 36 parts to characterize the random distribution characteristics of mortar.Mortar thickness has significant influences on PAC adhesion/cohesion properties,failure modes,and cohesive zone model parameters.Adhesion failure is observed when the mortar thickness is less than 0.9 mm or between 1.2-1.8 mm,while adhesion-cohesion mixed failure occurs when mortar thickness exceeds 1.9 mm,and other mortar thicknesses result in cohesion failure.Adhesion/cohesion strength increases with increasing mortar thickness in the same failure mode.Compared with the meso-scale finite element model without considering mortar random distribution(Model B),the crack initiation points of Model A and Model B are both adhesion failures,but failure locations are different.Model B primarily exhibits a single adhesion failure,while Model A demonstrates multiple adhesion/cohesion failure behaviors,which is more consistent with field complex adhesion/cohesion failure behaviors.The random distribution of mortar has significant influences on the adhesion/cohesion failure process,stress distribution,and crack propagation of PAC.Therefore,considering the random distribution of mortar can more accurately identify the weakest position of PAC adhesion/cohesion failure,and increasing the mortar thickness can delay the evolution of adhesion/cohesion failure.3 tabs,17 figs,40 refs.