Hongyu Ye

The bonding strength between the overlays of an airport asphalt pavement directly affects its service life. In this study, a finite element model of asphalt overlay on airport pavement of Juba Airport in South Sudan was established, and the elastic modulus of overlay, thickness of overlay, running state of aircraft, variation trend of interlayer shear stress under the action of load and temperature were obtained. The AHP-entropy method was used to calculate the combined weight of each influencing factor. The climate in hot and humid areas was further zoned, and a comprehensive classification of airport asphalt pavement overlay between hot and humid tropics was obtained. Four interlayer treatment measures (asphalt precoating, two oils and one aggregate, geotextile, and geogrid) and three interlayer materials (SBS-modified asphalt, ordinary hot asphalt, and SBS-modified emulsified asphalt) were designed and tested. Through shear test, wheel-load fatigue test, and pressurized seepage test, the variation trends of interlayer shear, crack resistance, and waterproofing under different combination schemes were obtained. Finally, the matching relationship between different working conditions and interlayer treatment measures was established. The results show that the actual working conditions of an airport asphalt pavement can be divided into three levels. Combined with the performance ranking of different materials and interlayer treatment measures, the recommended interlayer treatment measures for comprehensive classifications I, II, and III are two oils and one material + SBS-modified asphalt, asphalt precoating, or geogrid + SBS-modified emulsified asphalt or ordinary hot asphalt, and geotextile + ordinary hot asphalt, respectively. The working conditions in Juba Airport in South Sudan can be classified as comprehensive classification II, the recommended treatment measures for geogrid + ordinary hot asphalt.

Cement-stabilized macadam is commonly used in pavement base courses. The disadvantage of this material is that it easily cracks because construction vehicles cause irreversible fatigue damage to the pavement. Fatigue damage is caused by an insufficient number of maintenance days and overloading by construction vehicles. In order to analyze the influence of the number of maintenance days and overloading by construction vehicles, Miner theory and ABAQUS software were used, and an unconfined compressive strength test, an indirect tensile strength test, a bending tensile strength test, and a fatigue test were carried out simultaneously. The relationship between compressive strength and the splitting strength of water-stabilized macadam as well as compactness, water content, and temperature at different ages were determined. Fitting shows that the bottom tensile stress of the most disadvantageous layer increased with increasing subbase modulus, and its reduction rate increased slowly with the increasing of cement-stabilized macadam subbase thickness. The fatigue prediction equation for cement-stabilized macadam was obtained using bending tensile strength and fatigue tests. Subbase fatigue damage caused by different construction loads under different working conditions was calculated using Miner theory according to actual engineering data. Therefore, the number of pavement maintenance days should be increased. For harsh natural environments and strict time constraints, the design should increase the strength and thickness of the subbase material. When laying the base, overloaded vehicles should be limited, and the construction period of the loaded vehicles should be reduced to minimize road damage.