Study On Fatigue Life Of Asphalt Pavement Under Coupling Action Of Traffic Load And Temperature

Asphalt concrete pavement is directly exposed to the natural environment and bears the repeated action of various vehicle loads.Long term use practice shows that the temperature condition of asphalt pavement has an important influence on the bearing capacity and performance of asphalt pavement structure.The time of vehicle load acting on road surface is the time of subgrade bearing load decreases.Although the action time of wheels passing through the road is short,the cumulative action time is very long in the whole life cycle of the road structure.The coupling effect of periodically changing pavement structure temperature stress and traffic load results in pavement fatigue damage.Based on the actual loading condition of asphalt pavement structure,considering the influence of traffic load and environmental temperature,a numerical calculation model of asphalt pavement temperature field related to meteorological factors is established.The temperature at different depths of pavement structure is analyzed.Combined with the temperature division of Yunnan Province,the temperature distribution of asphalt pavement in Yunnan Province is obtained with 5 ? as the temperature interval.Among the 12 temperature ranges,the temperature time that can cause the performance deterioration of asphalt mixture is less than 9 days in a year,and the temperature of asphalt pavement in the temperature range of 10 ? 35 ? about 72% of the time.According to the classification method of expressway vehicle types,the traffic volume data of some expressways in Yunnan Province are collected.On the basis of field investigation,the occurrence frequency of expressway axle load with traffic characteristics in three different typical regions of Yunnan Province is analyzed.Based on the vehicle type of single axle and double wheel set,the proportion of 20 types of axle load in Yunnan Province is weighted,and the highway axle load representing different axle load characteristics is obtained road axle load spectrum.The results show that the interlayer bonding performance is significantly affected by the temperature,and the bonding performance at 60 ? is only 9% of that at 20 ?.The variation equation of interlayer bonding with temperature is obtained.Under different temperature conditions(10,20,30 ?),four stress ratios(0.5,0.4,0.3,0.2)were used to carry out fatigue tests on SMA-13,AC-20,AC-25 asphalt mixtures by indirect tensile test method.The fatigue failure law of asphalt pavement was analyzed,and the fatigue damaged equation of three typical asphalt mixtures was obtained.With the mechanical response distribution of asphalt pavement structure under different temperature conditions and different axle load levels is analyzed.With the change of external temperature in a day,the temperature stress of road structure has changed.The temperature stress of road surface has experienced a transition from low to high to high to low,and the temperature stress of road surface has the biggest change,increased by 3.69 times.Considering the change of interlayer bonding,under the coupling effect of temperature and traffic load,the temperature stress state of road structure changes from compression to tension.The stress at the bottom of pavement is always at the peak value,which is more than 30% higher than that under simple load.Based on the principle of fatigue cumulative damage,the fatigue times of asphalt pavement under different axle load levels and temperature ranges are calculated,and the fatigue life of asphalt pavement under different temperature zones is obtained.The results show that the fatigue life of asphalt pavement in different regions of Yunnan Province is quite different,and the total estimated service life of asphalt pavement in three regions is greater than the design service life.The fatigue life of asphalt pavement in hot summer and cold winter zone of Southwest Yunnan is only about 60% of that in cool summer and cold winter zone.The results show that the fatigue life of asphalt pavement is significantly affected by the interlayer bonding state.The interlayer bonding from completely continuous to completely smooth.The fatigue life of asphalt pavement structure in each temperature zone of Yunnan Province is greatly reduced,with an average reduction rate of 81.07%.The maximum reduction occurs in the hot summer and winter temperature zone of Southwest Yunnan Province,and the fatigue life is reduced from 12.03 years to 1.33 years.Through reducing the actual loading condition of asphalt concrete pavement,the fatigue behavior of asphalt pavement under different temperature range and different axle load distribution is obtained by combining theoretical research and numerical simulation analysis,field investigation and statistical analysis,indoor test and finite element simulation.The fatigue life of asphalt pavement is estimated more accurately through fatigue damage accumulation index calculation.It can effectively improve the accuracy of structure design and provide the basis for the maintenance decision of asphalt pavement.