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Characteristics of dynamic triaxial testing of asphalt mixtures .

机译：沥青混合料的动态三轴试验特性。

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摘要

Due to the increasing traffic loads and tire pressures, a serious detrimental impact has occurred on flexible pavements in the form of excessive permanent deformation once the critical combination of loading and environmental conditions are reached. This distress, also known as rutting, leads to an increase in road roughness and ultimately jeopardizes the road users' safety.The flow number (FN) simple performance test for asphalt mixtures was one of the final three tests selected for further evaluation from the twenty-four test/material properties initially examined under the NCHRP 9-19 project. Currently, no standard triaxial testing conditions in terms of the magnitude of the deviator and confining stresses have been specified. In addition, a repeated haversine axial compressive load pulse of 0.1 second and a rest period of 0.9 second are commonly used as part of the triaxial testing conditions. The overall objective of this research was to define the loading conditions that created by a moving truck load in the hot mixed asphalt (HMA) layer. The loading conditions were defined in terms of the triaxial stress levels and the corresponding loading time.Dynamic mechanistic analysis with circular stress distribution was used to closely simulate field loading conditions. Extensive mechanistic analyses of three different asphalt pavement structures subjected to moving traffic loads at various speeds and under braking and non-braking conditions were conducted using the 3D-Move model. Prediction equations for estimating the anticipated deviator and confining stresses along with the equivalent deviator stress pulse duration as a function of pavement temperature, vehicle speed, and asphalt mixture's stiffness have been developed.The magnitude of deviator stress, sigmad and confining stress, sigmac, were determined by converting the stress tensor computed in the HMA layer at 2" below pavement surface under a moving 18-wheel truck using the octahedral normal and shear stresses. In addition, the characteristics of the loading pulse were determined by best-fitting a haversine wave shape for the equivalent triaxial deviator stress pulse.The tandem axle was proven to generate the most critical combination of deviator and confining stresses for braking and non-braking conditions at 2 inches below the pavement surface. Thus, this study is focused on developing the stress state and pulse characteristics required to determine the critical conditions on HMA mixtures under the loading of the tandem axle.An increase of 40% was observed in the deviator stress when braking conditions are incorporated. A preliminary validation of the recommended magnitudes for the deviator and confining stresses on a field mixture from WesTrack showed consistent results between the flow number test results and field performance.Based on laboratory experiments, the critical conditions of different field mixtures from the WesTrack project and also lab produced samples at different air-voids levels were determined. The results indicate that the tertiary stage will occur under the FN test when a combination of a critical temperature and a given loading conditions for specific air voids content occurs.
机译：由于交通负荷和轮胎压力的增加，一旦达到载荷和环境条件的关键组合，就会以过度永久变形的形式对柔性路面产生严重的有害影响。这种困扰又称为车辙，导致道路不平整度增加，最终危及道路使用者的安全。沥青混合料的流量（FN）简单性能测试是从二十种方法中进一步选择评估的最后三种方法之一-在NCHRP 9-19项目下最初检查的四个测试/材料特性。目前，还没有指定关于偏斜幅度和限制应力的标准三轴测试条件。此外，三轴测试条件的一部分通常使用重复的0.1秒钟的haversine轴向压缩负载脉冲和0.9秒钟的静止时间。这项研究的总体目标是定义由卡车在热混合沥青（HMA）层中移动产生的负载条件。根据三轴应力水平和相应的加载时间定义了加载条件。采用圆应力分布的动态力学分析来精确模拟现场加载条件。使用3D-Move模型对三种不同的沥青路面结构进行了广泛的力学分析，这些结构在各种速度下以及在制动和非制动条件下承受不断变化的交通负荷。建立了预测方程，用于估算预期的偏斜应力和围压应力以及等效偏斜应力脉冲持续时间与路面温度，车速和沥青混合料刚度的函数关系。偏斜应力的大小，σ和σ围压分别为通过使用八面体法向和切应力转换在移动的18轮卡车下人行道表面下方2“处HMA层中计算出的应力张量来确定。此外，通过最佳拟合正弦波来确定加载脉冲的特性事实证明，在路面下方2英寸处，对于制动和非制动工况，串联轴能够产生最关键的偏转应力和约束应力组合，因此，本研究着重研究应力的产生。确定l下HMA混合物的临界条件所需的状态和脉冲特性合并制动条件后，偏斜应力增加了40％。初步验证了偏斜器的推荐幅度和WesTrack现场混合物的应力限制，结果表明流量测试结果与现场性能之间具有一致的结果。基于实验室实验，WesTrack项目以及其他领域的不同现场混合物的临界条件测定了实验室生产的不同气隙水平的样品。结果表明，当临界温度和特定气隙含量的给定负载条件组合出现时，第三阶段将在FN测试下发生。

著录项

  • 作者

    Ulloa Calderon, Alvaro.;

  • 作者单位

    University of Nevada, Reno.;

  • 授予单位 University of Nevada, Reno.;
  • 学科 Engineering Civil.Engineering Materials Science.
  • 学位 M.S.
  • 年度 2009
  • 页码 215 p.
  • 总页数 215
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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