| The typical climatic conditions in high altitude areas are low temperature,strong solar radiation,and large temperature difference between day and night.Year-round low temperature conditions and large temperature differences between day and night make asphalt pavements in high altitude areas continue to be subject to greater temperature stress,resulting in a large number of road surface temperature shrinkage cracks.The effect of vehicle load will cause the cracks to expand further,and then cause other serious diseases,which will seriously affect the traffic function and service life of the asphalt pavement.Therefore,it is of great significance to analyze the cracking under the combined effect of temperature and vehicle load on the asphalt pavement in high altitude areas and to conduct research on prevention and treatment.The research on asphalt pavement cracking mainly uses the interlayer tensile stress and shear stress to judge the expansion of the crack,but this cannot explain the stress concentration phenomenon at the crack tip,and there is a big gap with the actual situation;it is also applied to the pavement Most of the load considers the static load,which is not consistent with the moving load generated by the actual vehicle driving.In addition,when studying the comprehensive effect of temperature stress and load,the behavior of asphalt performance with temperature is rarely considered.In view of the above research questions,this paper establishes the temperature field and temperature stress field of asphalt pavement based on the measured weather and pavement temperature data at K3 357 on the Qinghai-Tibet Highway at an altitude of 5231 m.The stress intensity factor is introduced to further analyze the temperature based on the theory of fracture mechanics —The expansion form of cracks under the combined action of dynamic load;the influence of various factors on cracking is studied by adjusting the modulus of asphalt material,load size and moving speed,and combined with the lack of maintenance work of existing road maintenance teams,it is proposed to propose asphalt pavement cracks in high altitude areas Prevention measures.The main contents are as follows:(1)Studyed the temperature distribution laws of different depths under the measured road surface,and analyzed the correlation and hysteresis between the meteorological parameters obtained by the weather station and the road surface temperature.Studies had shown that the temperature at different depths has similar changes within a day,but the surface layer fluctuates widely while the base layer temperature is relatively stable;the effects of air temperature,solar radiation,and wind speed on the temperature field have a certain hysteresis,and the hysteresis time varies with the depth.Increase and increase;the temperature field is related to the temperature and solar radiation intensity,and is moderately related to the wind speed.(2)Based on the collected meteorological parameters,ABAQUS software package was used to build a temperature field model and the calculated results were compared with the measured results,and a temperature stress field model was established to study the temperature stress conditions under different temperature conditions.Research shows that the heat flow direction and temperature are consistent with the measured data,and the initial temperature field setting is different from the actual temperature of each layer,which leads to the difference of the temperature field in the early stage;the temperature stress field of low temperature weather is much higher than that of high temperature weather.(3)A three-dimensional model of transverse cracks on the belt road surface was established,and the influence of temperature-dynamic load on the cracking form was discussed,and the changes of type I and type II stress intensity factors were observed by adjusting the parameters.The research shows that the stress increases first and then decreases when the moving load approaches—compresses—away from the crack,and the temperature stress has a greater impact on it.Type Ⅲ cracking is difficult to occur.The cracks are mainly type Ⅰ and type Ⅱ cracking,and type Ⅱcracking is dominant.Asphalt material performance is affected by temperature,and it is more prone to cracking under low temperature conditions.Appropriately reducing the modulus of the upper layer,increasing the modulus of the lower layer,accelerating the vehicle speed and reducing the load will all help to slow down the cracking of the asphalt pavement.The road maintenance team needs to carry out road maintenance in a timely manner under low temperature conditions in winter to repair cracks as soon as possible. |
