Study On The Structure And Material Design Of Heavy Load Asphalt Pavement Based On Layer Function

With the rapid development of the national economy,the highway transportation industry has been developing vigorously,and the phenomenon of heavy load and overload has been increasingly prominent.As the main structural form of high grade pavement in China,asphalt pavement often fails to meet the requirements of heavy traffic during the design years,which lead to the occurrence of serious early damages.The frequent occurrence of rutting and cracks greatly shortens the service life of asphalt pavement.Therefore,according to the functional requirements of each structure layer,it is of profound significance to study the design of asphalt pavement structure and material combination which can resist the repeated action of heavy load traffic.First of all,through the investigation of the basic data recorded by the Weigh-in-Motion system of the Beijing-Shanghai Expressway,the traffic composition and the axle load characteristics were analyzed and the measured load spectrum of the traffic axis was drawn,then 120kN and 140kN were selected as the representative axle load of the overtaking and traveling lanes of the Beijing-Shanghai Expressway respectively;According to the data recorded by the asphalt pavement maintenance management and decision-making support system on the Beijing-Shanghai Expressway,the representative sections of heavy load were selected,and the rutting and transverse cracks were used as typical damages.The causes of the typical damages were analyzed from the aspects of heavy load traffic and the pavement structure form,which provides the basis for the selection of the heavy asphalt pavement structure type.Secondly,two kinds of pavement structure form of inorganic binder stabilized base asphalt pavement and asphalt binder class asphalt pavement were selected,and the influence of surface thickness,surface layer modulus gradient,heavy load and horizontal force on the mechanical response of asphalt pavement was analyzed by ABAQUS finite element software and elastic layered system theory.Taking the main design indicators of the asphalt pavement into account,the best thickness combination and surface layer modulus gradient recommendation scheme for all kinds of asphalt pavement structures have been obtained.By the sensitivity analysis,the key design indexes and design points of heavy load asphalt pavement were determined,which provide the basis for the design of heavy load asphalt pavement structure and material combination.Then,according to the characteristics of heavy load traffic and the causes of typical damages of Beijing-Shanghai Expressway,SMA-13,Sup-20 and Sup-25 graded asphalt mixtures were selected as materials in the upper,middle and lower layers.The road performance and mechanical properties of seven kinds of surface asphalt mixtures were tested by different experiments.The test results show that the pavement performance and mechanical properties of seven kinds of surface asphalt mixture can meet the requirements.With the addition of basalt fiber,a slight improvement was found in the high temperature resistance and low temperature crack resistance of the asphalt mixture.Although the effect of water stability was not obvious,the shear resistance and fatigue life were greatly improved.Finally,the pavement structure type was selected according to the mechanical response results,so as to give full play to the combination design principle of the layer function of each structure layer.Through the reasonable combination of the thickness of the surface layer and the measured modulus of the material,three kinds of pavement structures were recommended,including the conventional inorganic binder stabilized base asphalt pavement,the "thin surface"inorganic binder stabilized base asphalt pavement and the asphalt binder class asphalt pavement.According to the measured traffic parameters and surface material performance of Beijing-Shanghai Expressway,the recommended pavement structure was checked by goodpave software,and the design requirements of heavy load asphalt pavement can be met.The research results may be applied directly to the pavement maintenance and widening engineering of Jiangsu section of Beijing-Shanghai Expressway,and it is of great guiding significance to the construction of the new and rebuilt highway under heavy load traffic conditions in China.