The Research On Testing Method For Shear Performance Of Asphalt Mixture

Asphalt pavement will endure heavy shear stress in it's service life,but asphalt mixture's ability of resisting shear stress was not considered in the design process.As a result, shear stress failure and shear stress fatigue failure was easily occur with once or several times of traffic load repetition. At present, all kinds of test measuring the asphalt mixture's ability of resisting shear stress had their own shortcomings. Consequently, a test which can measure the asphalt mixture's ability of resisting shear stress and it's shear fatigue failure life, and has an obvious shear stress failure surface is necessarily designed.A test which has one kind of cone-shape failure plane was designed.With tridimensional finite element analysis, the stress status of the specimen was computated.According to the principal of third stress theory, the maximum shear stress plane was obtained. From the analysis of tridimensional finite element, we can see that:the cone-shape failure plane obtained from the test was the maximum shear stress plane, the direction of the maximum shear element was approximately the same with the direction of cone-shape failure plane. So we can draw a conclusion:the destory of cone-shape failure in designed test was due to the shear stress failure.The factors Influencing the maximum shear stress coefficient were analysised.The specimen height,the size of the axle head and the size of the ring when the shear stress coefficient had good stability were determined.Judging from the shape of destructive crack of the specimen: the crack shape of the specimen generated at the action of single axle penetration load in designed test was almost the same with the crack of asphalt pavement.The designed test was simple and easily operated. When the size of the ring is 0, the test was changed to the single axle penetration test;when the the size of the discharge head and the size of the ring were the same, the test was changed to the direct shear test. When the size of the discharge head and the size of the ring were adjusted, the test would have a cone-shape shear failure plane, this was the major advantages of the designed test.The shear stress value obtained from the designed test had good stability. The height transformation factor was definited to convert the non-standard specimen's shear stress to the standand specimen's.Combining compressive stress test the cohesion and intermal friction angle of the asphalt mixture were obtained. The factor influencing the asphalt mixture's ability of resisting shear stress were analysised. The test suggested that:The asphalt mixture's ability of resist the shear stress will drops with the increase of temperature.The asphalt mixture's ability of resist the shear stress will elevate with the increase of loading speed.The asphalt mixture's ability of resist the shear stress reached the maximum value when the asphalt-stone ratio was a bit less than the best asphalt-stone ratio. The asphalt mixture's ability of resist the shear stress was high when the cohesion of asphalt was big.The more amount of the coarse aggregate content were,the higher asphalt mixture's ability of resist the shear stress was. Finally,the shear fatigue life was measured by design test to return out the shear fagitue equation.