Unbound granular material specifications for road pavements in Australia are primarily based on physical material specification rather than mechanical characterisation. This simplified approach does not reflect the actual material performance under repeated dynamic traffic loads. There is a little information available on the influence of the local crushed rock properties and compacted layer properties on permanent deformation (PD). This study aims to characterise the local unbound granular materials in Victoria according to their PD behaviour under repeated loads and to develop a suitable shakedown criterion that could describe the PD of the tested materials to simplify the flexible pavement design. Repeated-load triaxial tests were conducted over several samples with a range of moisture contents, gradations, densities, and stress conditions. The laboratory test results showed that PD behaviour was influenced by several factors. In addition, the tested subbase-specified unbound granular materials reflect high PD resistance that is almost equivalent to base-quality unbound granular materials. This may indicate that current requirements for the subbase-quality unbound granular materials are over-prescribe. Moreover, as the existing shakedown criterion was not applicable for the multi-stage repeated-load triaxial test and the local tested materials, a new shakedown criterion and new boundaries are proposed based on the PD behaviour. In the proposed criterion, the shakedown ranges are identified based on the curve angle of the PD vs. logarithm of the number of loading cycles, and this new criterion was validated using several materials from existing literature. The local tested base and subbase materials can be assigned as Range A when PD < 1%, Range B when 1% < PD < 3%, and Range C when PD > 3%. The proposed criterion could provide a useful and quick approach to assess the PD of the unbound granular materials with both single and multi-stages of stresses.

中文翻译：

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未结合的粒状材料的新的破碎准则和永久变形特性

澳大利亚道路路面的未结合粒状材料规格主要基于物理材料规格，而不是机械特性。这种简化的方法无法反映出重复动态交通负荷下的实际材料性能。关于局部压碎岩石特性和压实层特性对永久变形（PD）的影响，目前掌握的信息很少。这项研究旨在根据在反复载荷下的局部放电性能来表征维多利亚州的局部未结合的粒状材料，并开发出一种合适的粉碎标准，该描述标准可以描述被测材料的局部放电以简化柔性路面设计。对多个样品进行了重复载荷三轴测试，这些样品具有一定的水分含量，等级，密度和应力条件。实验室测试结果表明，PD行为受多种因素影响。此外，经测试的指定基材的未结合粒状材料反映出较高的PD耐受性，这几乎等同于基本质量的未结合粒状材料。这可能表明当前对次基质量未结合粒状材料的要求过高。此外，由于现有的减振准则不适用于多级重复载荷三轴试验和局部测试材料，因此基于PD行为提出了新的减振准则和新的边界。在提出的标准中，根据PD的曲线角度与加载周期数的对数确定了击落范围，并使用现有文献中的几种材料对这一新标准进行了验证。当PD <1％时，可以将本地测试的基础和次基材料指定为范围A；当1％<PD <3％时，可以将范围B指定为PD；当PD> 3％时，将范围C指定为范围C。拟议的标准可以提供一种有用且快速的方法来评估单阶段和多阶段应力下未结合的颗粒材料的局部放电。