| Old cement concrete pavement with long-term use will appear a variety of diseases,on governance for their diseases, the original road paving asphalt layer directly is the most commonly used measures to repair. Due to the original pavement joint or other crack existed in the paving layer often with the effect of temperature and load and reflection crack generation. Reflective crack as the main diseases of paving layer, will seriously affect the road driving comfort and safety, therefore, in-depth understanding of reflective crack of asphalt layer evolution and extension mechanism is necessary.In this paper, on the basis of existing research, the reflective crack of asphalt layer continue to system study on the mechanism and evolution regulation, using the method of theoretical analysis and indoor experimental research methods to study and to explore the ability of reflective crack of asphalt mixture asphalt mixture reflection crack extension mechanism. Based on the evolution rule and mechanism of reflection crack, this paper mainly studies carried out the following aspects:1, According to the research status both at home and abroad for reflection crack,understanding can induce reflection crack influence factor, to understand the characteristics of reflection crack occurrence and its development, understand the current research status and existing problems of it is not clear;2, According to the theoretical basis of fracture mechanics and finite element method to cause reflective crack of asphalt layer and extension mechanism system is analyzed;3, Through finite element analysis software Ansys to establish calculate model paving layer in the vehicle load and temperature stress analysis and stress distribution under the action of both law and change;4, Draw lessons from the Texas transportation institute(TTI) development of CAM type Crack(Crack attenuation Attenuating Mixture) asphalt Mixture method to carry out the research. According to the low temperature bending test and immersion Marshall test and the sliding resistance test of mixture for road use performance test;5, To carry out the indoor Overlay Tester test research, the use of domestic advanced UTM-100 series of test equipment, the happening of the reflective crack of asphalt layer and extension mechanism were studied.Based on fracture mechanics analysis, Ansys software analysis, Overlay Tester test method to carry out the related research work, some useful conclusions are obtained:1, In under the action of traffic load and temperature load separately and together,the internal stress of asphalt layer and the change characteristics of the crack tip stress intensity factor, it is concluded that asymmetric load and temperature load on the impact is bigger. Other pavement structure itself characteristics of reflective crack and extended also to have certain effect;2, Study the asphalt layer thickness, modulus of asphalt layers, fracture length,vehicle axle load size, cooling rate, etc in a limited range change of crack of asphalt layer the influence degree of the stress intensity factor, the key that adds layer depth will not only affect the temperature type of reflective crack, and affect the shear reflection crack;3, Experiment it concluded that the crack resistance of asphalt mixture and the relationship between the temperature and the crack width, to a certain temperature range, the lower the temperature, crack resistance, conversely, the better; Within a certain range crack width, the width is smaller, the better the crack resistance,conversely, the worse;4, Test results of tensile stress in the analysis of asphalt mixture can be obtained the attenuation characteristics of the early cracking(33%) tensile stress attenuation attenuation speed faster, cracking middle(53% ~ 73%) tensile stress attenuation, the attenuation rate significantly slower, cracking late(73% ~ 93%) tensile stress attenuation attenuation speed is more slow. |
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