正应力条件下沥青混合料扭转剪切试验方法研究

Study on Torsional Shear Test Method for Asphalt Mixture under Normal Stress Condition

针对现有沥青混合料剪切试验方法的不足,对国内外沥青混合料抗剪性能试验方法进行研究分析,提出了一种新的正应力条件下的扭转剪切试验方法。其原理是通过千斤顶对试件均匀施加正应力,同时再通过齿条和齿轮将竖向力转化成扭矩,使圆柱体沥青混合料试件处于压剪状态。建立三维有限元模型进行理论分析,得出试件内部的剪应力分布,表明试件破坏状态为剪切破坏。对两种沥青混合料在不同温度和不同正应力条件下进行扭转剪切试验,结果表明混合料的抗剪强度随着温度的升高急剧降低,混合料的抗剪强度与正应力呈线性增长关系,符合摩尔-库伦强度理论。根据摩尔-库伦理论线性回归得到混合料的黏聚力和内摩擦角,将其与其他3种试验方法结果进行比较,表明该试验方法具有较好的可行性和可靠性,可以有效地评价沥青混合料剪切性能。

Considering the shortcomings of existing asphalt mixture shear test method, a new method of torsional shear test under normal stress based on the analysis of the test methods of the shear resistance of asphalt mixture at home and abroad is presented. The experimental principle is that normal stress is uniformly applied to the specimen through jack, and vertical force is transformed into torque by rack and gear, so that the cylinder~ asphalt mixture specimen is in the press shear state. A 3D finite element model is established to analyze the shear stress distribution in the specimen, it shows that the destruction state is shear failure. The torsional shear tests on 2 asphalt mixtures are conducted at different temperatures and under different normal stresses. The result shows that the shear strength decreases rapidly with the increasing of temperature, and the shear strength linear increases with the increasing of normal stress, it is in accordance with the Mohr - Coulomb theory. The cohesion and the internal friction angle are obtained according to the Mohr - Coulomb theory through linear regression, the results is compared with the results of other 3 test methods, it shows that the proposed test method has good feasibility and reliability, it can evaluate the shear performance of asphalt mixture.