Study On Structure And Material Adaptability Of Asphalt Pavement In High Altitude Region Of Guizhou

The Yunnan-Guizhou plateau and the surrounding regions are regarded as the high altitude areas which are loated in the western south of China. It shows the obvious plateau climate characteristics such as low temperature in winter,large temperature difference day and night,less temperature difference for a year,the long sunshine,the strong solar radiation,the clear wet and dry season and the frequent strong winds. Accordingly,the asphalt pavement in these regions often occurs premature aging,cracks and other pavement diseases. In view of the reflection crack universality and severity,the applicability of the semi-rigid base asphalt pavement in the high and cold area is subjected to question.In view of the severe climatic conditions,traffic load properties and service requirements of highways in high-altitude regions of Guizhou province,the behavior property and design method of asphalt pavements in high-altitude regions is systematically studied in terms of pavement structure and pavement material in order to present a reasonable design method theoretically and practically for asphalt pavement structure and material in high-altitude regions. Accordingly,the deficiency of the application of the current design specification in high-altitude regions can be made up.Firstly,the evaluation of general laboratory experiment of asphalt mixtures in high-altitude regions is introduced as well as the experimental study of nano-modified asphalt and fibers-reinforced asphalt mixture which are suitable for high-altitude regions with high performances. The result indicates the AC-13 is close to the mid-value and the improvement of asphalt content is suitable for high-altitude regions. The asphalt-aggregate ratio can be increased if allowed in order to meet higher standards of water stability,low-temperature crack resistance and fatigue resistance. The low-temperature crack resistance of asphalt mixtures can be significantly improved by using higher grade asphalt. The thickness of asphalt surface has less i MPact on cracking than subgrade and asphalt materials. The performance of asphalt mixtures can be remarkably improved through adding fibers. The polyester fiber and FORTA®AR fiber have better performances than that of lignin fiber.Secondly,in order to study the performance of waterproof and anti-crack base further,the A-70 asphalt is used with three different grading types(near to the upper limit,median and lower limit of the grading range) to analyze the i MPacts of mineral aggregate gradation on pavements performance such as the water stabi lity and low-temperature crack resistance of waterproof and anti-crack base,in order to select the suitable grading type for waterproof and anti-crack base. The affect of grading types and asphalt proportion on water stability is tested by Hamburg wheel tracking test. The result shows that AC-10 asphalt mixture has better performance than that of Strata stress-absorbing interlayer and is suitable for constructing the waterproof and anti-crack base.Then,to accurately test the crack resistance of different kinds of pavement materials and put forward a new device which can simulate the mechanism of reflection crack,the experiment is conducted in order to evaluate the crack resistance and anti-fatigue ability of different kinds of materials and improve the exis ting methods of proportioning design. Further,The mix proportion design performance of asphalt mixtures is proposed based on the results of Hamburg wheel tracking rutting test and Overlay tester,considering the high-temperature deformation resistance and low-temperature crack resistance of asphalt mixtures.Next, two kinds of pavement structures are proposed which are inverted composite base structures,waterproof and anti-crack base structure. Then,the mechanical behavior of the pavement structure is simulated through the numerical method. The results indicate that the tensile stresses appear at the bottom of surface course when inverted composite base structure is subjected to the load action,and increases nearly linearly with the increase of axle load. The bottom of graded crushed stone layer is in the compression situation all the time and the tensile stress on the base course is significantly smaller than traditional semi-rigid base structure. Significantly, the waterproof and anti-crack base can significantly delay the emergence and development of crack. Furthermore,the stress intensity factor on the crack tip at the bottom of the asphalt concrete layer falls down with the decrease of the modulus of waterproof and anti-crack base. The rutting won’t be increased for the pavement which has the waterproof and anti-crack base because it does not give contribution to the rutting increase.Finally,for presenting the more reasonable and reliable design methods of pavement structure,the existing design standards of asphalt pavement is adopted to design different kinds of asphalt pavement structures,then the prediction method of fatigue accumulated damage under load(Miner rule) is used to verify the structure. The result indicates that the structural layers in semi-rigid pavement structure with thick asphalt have smaller fatigue damage factor,thus,this kind of structure is the optimal in terms of fatigue life.