交叉口沥青路面剪切损害机理及剪切

试验方法研究

Research on mechanism of  shear destructions of the intersectional asphalt pavements and method of  shear tester

研究生：冯俊领

指导教师：郭忠印教授

二〇〇七年六月

摘要

近年来，随着交通量的快速增长、轴载不断增加，交叉口沥青路面在夏季高温季节产生严重的拥包、推挤和车辙等病害，基本上每两年就要铣刨一次重新摊铺，主要由于沥青混合科的设计过程中忽略了对其抗剪强度的检验，采用原有路面抗剪控制指标已不能有效的解决沥青路面剪切病害问题。

论文首先实地调查城市道路交叉口沥青路面的剪切损坏特征和交通状况，掌握交叉口沥青路面在频繁启动、制动条件下发生损坏主要特点及典型特征，为分析交叉口沥青路面剪切损害机理提供实例。

其次，对交叉口沥青路面剪切损害机理进行研究，采用三维有限元分析方法针对交叉口沥青路面的特点，采用垂直荷载和水平荷载共同作用形式，进行多种工况下不同路面结构的力学响应分析，以研究路面结构的力学响应及了解路面结构的剪应力场的分布规律。得出以下结论：水平荷载对沥青路面剪应力、表面的拉应力的影响最大，对路表面弯沉、各结构层的层底拉应力的大小基本上没有影响。沥青路面的结构类型、模量、厚度、环境温度等对面层最大剪应力影响不大，关键决定于水平力系数。但高温条件下由于沥青混合料温度敏感性材料，温度对沥青混合料的抗剪强度影响很大，所以，高温条件下交叉口沥青路面的剪切破坏主要是由于沥青混合料的高温抗剪切强度不足而产生的。

然后，在目前国内外沥青混合料抗剪试验方法研究分析的基础上，本文提出了一种全新的评价沥青混合料的抗剪强度的方法，即同轴剪切试验方法，同轴剪切试验不但方法比较简便，而且试件受力特点符合路面的实际状况。建立同轴剪切试验模型的三维有限元模型，着重对同轴剪切试验试件力学响应进行分析然后对同轴剪切试验试件受力特点进行有限元分析；根据试件的受力特点提出沥青混合料抗剪强度的指标，采用三轴试验抗剪强度指标进行对比验证。

最后，采用同轴剪切试验来研究不同温度状态、不同空隙率的沥青混合料抗剪性能。对不同试验温度条件下沥青混合料抗剪性能进行对比分析。采用重复加载同轴剪切试验来研究沥青混合料的剪切疲劳性能。在参考国内外疲劳模型的基础上，提出高温条件下沥青混合料剪切疲劳方程，采用车辙试验进行验证，得出其模型是合理的，可见同轴剪切试验能够有效、快捷的评价沥青混合料的抗剪性能。根据当前交通条件下交叉口路面实际受力状况，提出相应的沥青混合料抗剪强度评价标准。

关键词：沥青路面，交叉口，拥包，推挤，车辙，损害机理，剪应力，同轴剪切试验，抗剪强度系数，抗剪强度，剪切永久变形，三轴试验，车辙试验，分层叠加，抗剪评价标准

ABSTRACT

In recent  years，shear  destructions such as pushes/rut，arise on the crossing asphalt pavements with the volume of traffic  growing greatly and the axial load increasing．Surface had to be rebuilt every two years，because mainly the shear  strength examination of asphalt mixes had been neglected in the design  process，and the  original shear control index call not prevent effectively shear destructions．

Firstly，based on field investigating  shear damage phenomena and volume of traffic conditions on intersection，shear destruction types and  typical characters were got，so as to prepare for analyzing the mechanism of shear destructions  on the road intersection．

Secondly，the mechanism of shear  destructions on the road intersection analyze by three dimensional finite  element analysis method．In view of the intersection asphalt pavements characters，the mechanics working state  and responses of asphalt pavements under the vertical horizontal loading  together．Drawing  some following conclusions，such as：the horizontal load greatly influences shearing stress/the superficial  tensile stress，but  little influences the surface deflection and tensile stress at bottom of  layers；the  structure type of asphalt pavements，module，thickness，the ambient temperature has some effect on the biggest shear  stress of pavement，the key is the horizontal force coefficient；because the asphalt mixes is  the temperature susceptible material，temperature influence greatly on shear stress of it，and the high temperature anti-shearing  strength is so enough that shear destructions arise on the intersection  asphalt pavements．

Thirdly，based on research on the  shear test method in the domestic and foreign at presently，the co-axial shear test，one newly shear test method，is first developed．The method is not only  operating simple，moreover  the test sample stress characteristic conforms to actual road conditions．The mechanism responses on  the test sample analyze by three-dimensional finite element analysis method，and the coefficient of shear  strength is first developed．What’s more，the triaxial test results confirm that the co-axial shear test  results are correct．

Finally，the co-axial shear test  studies the anti-shear strength of asphalt mixes at the different temperature  and the different percentage of voids．The repeated load co-axial shear test study the anti-shear fatigue  performance，and  the shear fatigue model of asphalt mixes under the high temperature condition  is got based on the study to the domestic and foreign fatigue models，the models is confirmed  reasonable by the wheel-track test．So the co-axial shear test call effectively，quickly appraise the anti-shear  performance of asphalt mixes．Furthermore，based on the intersectional asphalt pavements’ actual stress  condition，a  corresponding criteria on the anti-shear performance of asphalt mixes is  proposed．

Keywords：Asphalt pavements，Intersections，Ruggedness，Pushes，Rutting，Mechanism，Shear stress，Co-axial shear test，Anti-shear strength coefficient，Anti-shear strength，Permanent shear deformation，Triaxial test，Wheel-track test，Combination of sublayer  deformation，Appraising  criteria