Study On Temperature Field And Temperature Fatigue Of Asphalt Pavement In Alpine Region

In the alpine region of China,because of the low temperature and the large temperature difference between day and night,the temperature field of asphalt pavement changes violently,so the pavement is prone to temperature stress cracking and temperature fatigue,which seriously affects the service life of the asphalt pavement,and becomes a problem hindering the development of the asphalt pavement in the alpine region of China.At present,most scholars often use numerical simulation to study the temperature field and temperature stress of asphalt pavement.However,due to the incompleteness of meteorological data acquisition and improper selection of pavement thermal parameters,the analysis results are quite different from the actual results.On the other hand,the existing temperature field prediction formula also has the limitations of application scope or calculation complexity.Therefore,it is very necessary to optimize the calculation formula or method of temperature field and temperature fatigue of asphalt pavement in alpine region.In this study,the accurate pavement thermal parameters were determined through statistical analysis and comparative analysis.The pavement finite element model was established,and the key factors affecting the temperature field of asphalt pavement were analyzed by using the climate data of alpine region.On this basis,a simple form of temperature field prediction function of asphalt pavement was proposed,and the method of directly calculating temperature stress and temperature fatigue using the temperature field prediction formula was discussed.The main research contents are as follows:(1)Statistical analysis and value selection of thermal parameters of asphalt pavement materialsFirstly,the test results of thermal physical parameters of asphalt mixture,inorganic binder,granular material and soil base at home and abroad were collected,Then,according to the number of test samples and the types of influencing factors of each thermal parameter,the thermophysical parameters are divided into two categories,which are analyzed by statistics and discussion,respectively,so as to propose the value range or calculation formula of each thermal parameter.(2)Establishment and verification of temperature field model of asphalt pavementDuring the establishment of the model,the typical asphalt pavement structure was selected,and the thermal parameters of the pavement materials in the model were given by using the research results of the statistical analysis of the thermal parameters of the asphalt pavement materials.Then the climatic boundary conditions and the climatic parameters are determined,and the grid was divided according to the time increment principle of the finite element transient thermal analysis.Finally,the temperature field model of the asphalt pavement was calculated iteratively compared with the theoretical solution.The results show that the temperature field of the model is accurate after 10 iterations.(3)Analysis of the factors influencing the temperature field of asphalt pavementThe influencing factors of the temperature field of asphalt pavement can be divided into two parts: climate and pavement structure.For the influence of climate parameters on the temperature field of asphalt pavement,the orthogonal analysis was carried out with wind speed,total solar radiation,sunshine time,daily average temperature and daily temperature difference as factors,and the maximum temperature difference on the road surface,the maximum negative temperature gradient,the average temperature and the maximum temperature difference at the bottom of asphalt layer and the maximum positive temperature gradient as test indexes.For the influence of pavement structure on the temperature field of asphalt pavement,the influence of different thickness of asphalt pavement,different types of base course and different materials of upper layer on the temperature field of asphalt pavement surface was analyzed by this paper.When the asphalt layer thickness is different,the temperature at the same depth from the road surface is the same.When the asphalt layer thickness is not changed,the pavement temperature fluctuation decreases with the increase of depth;The influence of semi-rigid base and flexible base on the daily temperature difference of asphalt pavement is not significant;Under the same climate condition,at the depth of 2cm,the daily temperature difference of asphalt layer of OGFC,AC and SMA is almost the same.In addition to the depth of 2cm,within the whole asphalt layer,the closer the asphalt layer is to the road surface,the more obvious the difference between the daily temperature difference of the three pavement materials is.Among them,SMA pavement has the smallest daily temperature difference.Therefore,SMA mixture can be preferred for the upper layer in the area with large temperature difference.(4)Prediction formula of temperature field of asphalt pavementBased on the double sinusoidal function model with daily average temperature and daily temperature difference and the key influencing factors of pavement temperature field,and considering the difference between temperature and pavement temperature,the decreasing effect of pavement temperature amplitude with depth,and the lag effect of temperature field with depth,the temperature field prediction function of asphalt pavement was designed,and the temperature field prediction function was regressed and fitted by substituting different climate parameters and pavement thickness.Finally,the temperature field prediction model with the parameters of daily average temperature,daily temperature difference,time and pavement depth was proposed.(5)Temperature stress and temperature fatigue analysis of asphalt pavementThe temperature field stress and temperature fatigue of asphalt pavement in Ali,Lhasa and Harbin were analyzed,The temperature stress of asphalt pavement in alpine region is mainly considered in spring and winter;the temperature stress of pavement in alpine region decreases with the increase of depth,so the temperature stress or temperature fatigue damage is most likely to occur on the pavement surface.For alpine regions,the greater the daily temperature difference is,the more obvious the temperature fatigue is.In this study,thermal parameters of asphalt pavement were analyzed by statistical and comparative methods,which provides a reference for how to select thermal parameters of asphalt pavement in the numerical analysis of temperature field and thermal stress,so as to reduce the error caused by improper parameter selection.The proposed temperature prediction formula has the characteristics of satisfying engineering requirements,wide application range and simple calculation.This formula is used to calculate the pavement temperature stress and pavement temperature fatigue in the alpine region.The calculation idea can provide some reference for the engineering design of asphalt pavement in the alpine region.