Research On Prediction For Fatigue Life Of Asphalt Pavement Based On Fatigue Cumulative Damage

The performance degradation of asphalt pavement often attributes to opinion that pavement design based on mechanical-empirical method has large disparities between actual situations.The design procedure in domestic and diversification of highway road structure are contradictory,that results in a great quantity of severe distresses which causing tremendous economic loss and adverse influences.In our country,pavement construction have implemented mechanistic-empirical method to design for a long time.At present,the development tendency has transformed to multifarious pavement structure from sameness semi-rigid structure.Many researches have been carried out considering the most important two factors:dynamic vehicle load and climate environment to discuss the distribution of structural mechanics responses for flexible base asphalt pavement under different climates and wheel loads.In this paper,the fatigue failure model of flexible pavement has been established through indoor test and theoretical analysis which conducted a method for pavement service life prediction based on the cumulative damages at various climate parameters and different axle load levels.This research provides the basis for pavement design or management.The main research results are as follows:? The effect of air temperature,solar radiation,wind speed and sunshine hours based on in-situ measuring meteorological data were presented to be meteorological factors affecting the temperature distribution in asphalt pavement.The heat conducton equation based on heat transfer theory has been derived to establish unstable status temperature field for asphalt pavement under the four factors previously mentioned.Base on the finite difference equation with implicit expression,numeric solution of internal nodes and boundary nodes have been calculated to compare with pavement temperature data measured in in-situ observation of Dali,Yunnan.By assessment of asphalt pavement temperature interval,the estimation of asphalt pavement fatigue service life and the temperature climate district for pavement in Yunnan province have been proposed.The distribution of the temperature along with depth of pavement structure derived from the calculated results have been plotted in according with the different surface temperature arrangement.? More than thirty toll stations of three expressways with different transport charateristc in Yunnan province have been investigated.The proportions of different axle load types and vehicle models were obtained by statistical analysis of three typical samples investigated in Kunshi highway road.This study represented the uniaxial wheelset employing calibrated frequency of different axle loads,as well as the representative distributions of tandem axle and tridem axle loading which considering the switch of charging axles.? Fatigue failure mechanism for the asphalt mixture was described,in which the fatigue damage developing stages and influence factors on the fatigue behavior of asphalt mixture proposing.The indirect tensile test of three typical concretes,including AC-13,AC-20 and AC-25,were carried out at 10,20,30?.Subsequently,the influence of different temperatures about fatigue life,fatigue characteristical parameters were discussed.The test results were analyzed by weibull distribution function applied three parameters to reflect the influences of different characteristics like stress level or test temperature on fatigue performance.The investigations verified that the equation of unique-strain fatigue curves and strain fatigue surface equation to predict fatigue properties of different materials.Analysis results show that there is good linear relationship between stress level and fatigue life in double-logarithms coordinates.Fatigue life and the sensitivity about stress level were also decrease in same stress levels condition as the temperature increased.The use of unique-strain fatigue curves eliminates the influence of the temperature on the fatigue behavior.Unique-strain fatigue equation could be obtained from the test results in different temperatures.Also proved that is reasonable to suggest fatigue surface equation to predict the fatigue characterization of asphalt mixtures in different conditions.? Three types of typical asphalt pavement were constructed in full scale indoor test.To investigate the dynamic response characteristics of pavement,an in-site sensor is developed to determine strains implanted in structures.Using repeated vehicle load as the applied loading to study the mechanical responses of asphalt pavement under actual traffic load,the comparison between FEM simulation model and measured mechanical responses proved that the validity and consistency of the numerical simulation method.? A new model for asphalt pavement service life prediction was established based on fatigue cumulative damage theory.Taking climate division II area for an example,transverse strain in the bottom of asphalt surface layers have been calculated in different temperature divisions and different axle load levels.The cumulative fatigue failure tolerance in design period has been suggested basing on the fatigue prediction model from laboratory tests of different asphalt mixtures.Then,the fatigue limit design of asphalt pavement were presented which using the service life prediction model for highway pavement in various climate divisions.