The Temperature Adjustments For Dynamic Deflection And Back-calculated Moduli Of AC Pavement

The stiffness or modulus of asphalt concrete(AC) is very temperature-sensitive.Routine deflection test results must nearly always be adjusted to represent the deflection at a standard temperature or some other reference temperature.Also, the back-calculated modulus must be adjusted to the modulus expected at some selected reference or characteristic temperature for the section being analyzed.A number of procedures have been developed to adjust the deflections under the load plate and backcalculated asphalt moduli for temperature;however, most are based on limited data or for earlier deflection equipment, such as the Benkelman beam, especially in china, the temperature adjustment relations for dynamic deflection and backcalculated moduli based on the falling weight deflectometer (FWD) aren't still established, and are urgent need for sloved.How to define the pavement temperature is the first problem need for solve for performing the temperature adjustment of pavement dynamic deflection and backcalculated moduli. For AC pavements are exposed to nature and effected by nature condition momently, especially by air temperature, those lead to the complex distributions of AC pavement temperature field. So studying the temperature field of AC pavement and development the prediction model for pavement is the precondition for the temperature adjustment of dynamic and backcalculated.In this paper, at first, the temperature field of AC pavement is studied by field experiment and numerical simulations modeling respectively, then the relations between pavement dynamic deflection, backcalculated moduli and pavement temperature are studied, at last, the temperature adjustment relation for pavement dynamic deflection and backcalculated moduli based on FWD are developed in china. Specific work done in this paper is as follows:(1) The study of finite element simulation on AC pavement temperature fieldThe distribution regularities of AC pavement temperature field are studied by finite element model, and the comparison and verification with actual measured temperature show that the stimulation results are appropriate.(2) The study of actual measured temperature field of AC pavementTaking the typical structure of AC pavement as the observation object, a kind of detailed method for temperature field research is put forward. Based on the abundant measured temperature data, the regularities of distribution of asphalt pavement temperature field is studied in detail, and the dependency relation between the air temperature and temperature field is discussed with regression analysis. Thinking about the effect difference to asphalt pavement temperature field which applied by temperature rising period and temperature falling period of air, the dependency relation between air temperature and different temperature changing periods are researched respectively, at last, the prediction models on asphalt pavement temperature which based on different temperature changing periods are established. The comparison between measured and predicted pavement temperature indicates that these models are equipped with comprehensive applicability and excellent accuracy.(3) The study of temperature correction for pavement deflection based on FWDBy using the falling weight deflectometer (FWD), the dynamic loading tests on different thickness of AC pavement in different temperature are performed, and the relationship of pavement deflection and its represent temperature are studied. The investigation results show that the effects of temperature on dynamic deflection of AC pavement are significant, and the thickness of asphalt mixture is also another important influence factor.(4) The study of temperature correction for pavement back-calculated modulus based on deflection basinsOn the base of actual measurement deflection basins, the structure layer moduli of asphalt pavement are back-calculated by the system identification and GA combination algorithm, then the corresponding relation between the back-calculated moduli and AC representative temperatures are analyzed, the relevant temperature correction equations of back-calculated moduli are developed.(5) The study of dynamic deflection and it's coupling with temperature field of AC pavement based on finite element modelEstablishing the three-dimensional finite element model of AC pavement based on the experiment, and then the validity of finite element model is verified by comparing with the actual measured results.At last, the effects of surface thickness, surface modulus and base thickness, base modulus, soil strength and loading time to dynamic deflection of AC pavement are studied on the basis of finite element model. With reference to relevant literatures, the functional relationship between modulus of elasticity, coefficient of thermal expansion, and Poisson's ratio and temperature are fitted, then the temperature-structural coupling finite element model is established. Base on the finite element model, the effects of temperature on dynamic deflection of AC pavement are studied,the calculation results show that the effects of temperature on dynamic deflecton of AC pavement are significant.At last, taking the surface thickness into account, the maximum deflection changing trends of different thickness AC pavement under various temperature conditions are studied, and the temperature adjusted relations for various thickness AC pavement deflection are developed.The comparison between measured and calculated valuses indicates that the models are valid.