沥青混合料剪胀行为研究

Research on Shear Dilative Behavior of Asphalt Mixture

采用UTM-25多功能材料测试系统以及特制的径向应变测试装置进行沥青混合料的单轴等应变率压缩试验，分析了30，40，50，60℃下沥青混合料应力（轴向）、应变（轴向、径向、体应变）、加载时间之间的相互关系，研究了沥青混合料的剪胀机理．结果表明：沥青混合料剪胀性与温度相关．在沥青混合料体应变随加载时间变化过程中，当温度为30～50℃（低于沥青软化点）时，受荷沥青混合料初期表现为剪缩，随着加载时间的增大，很快表现为剪胀；当温度为60℃（高于沥青软化点）时，受荷沥青混合料一直发生剪胀，未出现剪缩．沥青混合料各向异性、沥青混合料颗粒单元体咬合松弛以及沥青对混合料的润滑作用（尤其当温度超过软化点时），都导致了沥青混合料剪胀的产生．

The uniaxial compression tests with equal strain rate were carried out using the UTM-25 multi- functional material test system and specially designed radial strain test device. The relationships between the stress（axial direction）, strain（axial, radial and volumetric strain） and loading time were analyzed at 30, 40, 50, 60℃ for further studying the shear dilative mechanism of asphalt mixture. According to test results, the shear dilative behavior of asphalt mixture is temperature dependent. On the process of volu- metric strain change with loading time, the asphalt mixture in beginning period of applying load shows shear shrinkage, but with loading time it soon exhibits shear dilation under the softening point of asphalt binder. There is no shear shrinkage when the whole process is done upon the softening point of asphalt binder. The dilative behavior of asphalt mixture is caused by the anisotropy property of asphalt mixture, the looseness of interlocks between particle elements in asphalt mixture and the lubrication provided by as- phalt for mixture, especially when the temperature is higher than softening point of asphalt binder.