Research on Pumping Effect in Base-Course or Subgrade on Rutting Behavior of Asphalt Pavements

本研究的目的是从基层或路基的泵送现象的角度，建立表面层裂缝发生后车辙行为突然增加的分析技术。本研究中各实验和分析得到的主要信息如下：1。利用自制的小比尺模型试验设备进行重复板加载试验：不论是碎石基材还是砂石基材，根据试验条件的不同，饱和状态下的板加载沉降量都比湿状态下的沉降量大2 ~ 4倍。仅就基材而言，确定其原因是泵送现象的发展及其发展领域。利用现有的重复三轴试验设备进行材料表征试验：饱和状态和湿状态的弹性和永久变形特性无显著差异。因此，假设与泵送区域内的土壤元素已经达到静态破坏的土壤元素相对应，尝试进行材料表征。结果近似于松散态材料的特性。重复板加载试验结果分析：湿状态迭代有限元法分析结果较好，饱和状态分析结果略低于试验结果。这被认为是由于加载板尺寸小，不稳定，忽略了试样变形的增加，直到达到静态破坏等。试验路面车辙分析：尽管上述分析结果存在不足，但将上述分析技术应用于试验路面取得了良好的效果。这表明了原位路面条件的复杂性。

The objective of this research is to establish the analytical technique for the sudden increase in rutting behavior after the occurrence of surface layr cracks, from the viewpoint of the pumping phenomenon of the base layr or the subgrade. Major information obtained from each experiment and analysis in this research are listed below :1. Repeated plate loading tests using the small scale model test equipment manufactured : For both crushed aggregate as base material and masado as subgrade material, the settlements of the saturated state under plate loading were 2 to 4 times bigger than those of the wet state, depending on the testing conditions. For only the base material, confirmed as the causes for this were the development of the pumping phenomenon and its area of development.2. Materials characterization tests using the existing repeated triaxial test equipment : The resilient and permanent deformation characteristics of the saturated state and the wet state did not show any remarkable differences. Materials characterization, therefore, assuming to correspond to those whose soil elements within the pumping area had already reached static failure, were attempted. The results were approximately similar to the characteristics of loose state materials.3. Analysis of repeated plate loading test's results : The analytical results using the iterative finite element method of the wet state were comparatively good but the results of the saturated state were slightly lower than the experimental results. This is thought to be due to the small size of the loading plate which are unstable, the disregard of the increase in the specimen deformation until it reached static failure, etc.4. Rutting analysis of test pavements : In spite of the inadequacy of the analytical results explained above, the application of the above analytical technique to test pavements showed good results. This suggests the complexities of the in-situ pavement conditions.