Research On The Refinement Of Axle Load Conversion Coefficient Of Asphalt Pavement Based On Measured Axle Load Spectrum

With the rapid development of China's national economy in recent years,the traffic volume of transportation and passenger transportation has increased rapidly,and overloading and heavy-haul vehicles have also increased Since September 2017,China has adopted a new road asphalt pavement design code,proposed a new design indicators,to a certain extent,to make up for the original specification in the axle load conversion deficiencies,but there is still room to continue to improve.In this paper,on the basis of the existing specifications of asphalt pavement design,combined with the measured axial load data,the research range of enlarging axle load conversion is 100kn-500kn,and the design reference value of corresponding axle load conversion coefficient is given.The main research contents are as follows:(1)In recent years,some high-speed traffic monitoring data in China were collected,and the development trend of heavy traffic in our country was preliminarily understood.Through the dynamic weighing system(WIM),the relevant traffic data of a highway section of the meihe river,river dragon and jiangsu province in guangdong province were sorted out.Through the analysis of the axle load spectrum,the traffic status of Highway and the main distribution range of axle load are obtained.Jiangsu Province within the Monitoring section,the 15-type car,125-car,157-type car corresponding to the specification of the definition of 4 class vehicles,7 categories of vehicles and 9 categories of vehicles,the measured overload rate of more than 90%,the actual full load rate is far greater than the standard recommended 30%?50%.The ratio of 125-type and 157-type vehicles with the average uniaxial axle load of more than 200kN is greater than 50%.(2)Based on the measured axle load spectrum,15 kinds of pavement structures were selected for four kinds of design indexes,and the axle load conversion coefficients of three kinds of asphalt pavement structures under different axial loads were analyzed by finite element software,and the relevant data were fitted.The results show that for the same design index,different axle-load conversion coefficients should be adopted for different surface layers of asphalt pavement,rigid,semi-rigid and flexible base.Based on the fatigue equivalent axle load conversion coefficient of asphalt mixture layer,it is advisable to use linear function related to axle load size for semi-rigid base and rigid base course;Based on the axle load conversion coefficient of the stability layer fatigue of inorganic binder,it is advisable to adopt the linear function related to the axle load size and the equivalent axle load conversion coefficient based on the permanent deformation amount of the asphalt layer,The upper layer should take 3.0,the middle layer should take 3.5,the following layer should take 4.0;Based on the equivalent axle load conversion coefficient of the roadbed top vertical compressive strain,it is not affected by the road structure combination and the axle load size,and is consistent with the canonical value.(3)According to four kinds of design indexes,the axial coefficients of the double and triple axes of the three kinds of asphalt pavement structures corresponding to the axle load conversion coefficients are calculated and analyzed by the finite element software Ansys.For example,based on the asphalt mixture layer bottom pull strain equivalent triple axis coefficient,semi-rigid base Road to take 3.57,flexible base road to take 2.86,rigid base road to take 1.42.The results of the study take into account the difference between the axle load and the pavement structure,and obtain the detailed parameters for the conversion of the asphalt pavement axle load,which can provide a reference for the related design in the future.