The Structural Analysis And Research On Composite Base Asphalt Pavement

Currently, the two main forms of pavement in domestic are cement concrete and asphalt concrete, while base course construct is dominated by semi-rigid material. However, with the emergence and worsening of overloading, the disadvantage of semi-rigid base course becomes much more apparent. And the damage appears earlier, even in the preliminary stage, disease such as rutting, pit, cranny occurs. As a result, the lifespan of highway has been shortened dramatically. Some sections with large acreage have to be repaired or rebuild in advance, thus leading to heavy economic loss.In order to deal with the limitations and diseases caused by semi-rigid base course, this thesis takes the foreign perpetual pavement design concept, proposing composite base construct, i.e., a new base course with semi-rigid base course as its subbase and asphalt macadam or graded macadam upbase.This thesis attaches itself to actual engineering, to study the mentioned structure by calculation. It's mainly in the following areas:First, it adopts current deflection index and flexural tensile stress method, AASHTO method and AI method making construction checking and contrastive analysis, to cope with the changes during the process of pavement construction design. All the calculation results is satisfied with the design requirement,but there is a certain deference.Second, comparing these three designing methods'application field and advantage and disadvantage, we come to the conclusion from comprehensive evaluation that our domestic designing method is not suitable for composite base asphalt pavement.At the same time , when calculates the allowed tensile strain, its due to the nature of the material as to change,and it related on the standards,material and the determination of parameters of abroad,and it is different with our country.So the AASHTO method is not suitable.Third, according to the analysis of calculation results of BISAR,the road construction which the thesis mentioned is not the perpetual pavement. Currently,The requirement of perpetual pavement structure is not regulated,but refered the domestic information,the flexural strain of the bottom of asphalt layer is below 120με,and the top of subgrade compressive strain is below 280με. Adding the thickness of asphalt layer is one method of fitting the standard of perpetual pavement construction.Fourth, according to the actual engineering and the differrent roles of each layer, the thesis determines the material and gradation of the main construction layers of the pavement,and then detects the road performance of surface layer asphalt mixture.The result of data indicates that the performance is superior, the material selection is reasonable and the gradation is suitable.Finally, the scene test after completion of surface layer shows that all the indicators are in line with the design standards.