Freezing Prediction And Multi Field Coupling Effect Analysis Of Asphalt Pavement Between Tunnels In Seasonal Freezing Area

The phenomenon of pavement icing often occurs in seasonal freezing areas in winter,and the proportion of bridges and tunnels in southwest mountainous areas is high.Due to the "white hole" effect at the junction of tunnel mouth and pavement between tunnels,this section is very prone to traffic accidents.It is of great practical significance to ensure the road safety between tunnels in seasonal freezing area by fully analyzing the influencing factors of asphalt pavement icing and establishing a multi physical field coupling model with high accuracy,simple operation and can be used to reflect the freezing state of asphalt pavement between tunnels in seasonal freezing area.At present,the research on asphalt pavement icing is still based on historical meteorological data or laboratory simulation data to predict the occurrence of icing,which takes a lot of time,and the data is discrete.The research on the icing process of asphalt pavement between tunnels in seasonal freezing area starts late,and the reference numerical model is limited.In view of the above problems,the following researches are carried out in this thesis.Based on the heat conduction theory and aqueoglacial phase change theory,the phase change heat transfer equation is derived,and the icing prediction model is established through general finite element analysis software.Our team has independently developed a set of test system for indoor ice simulation,and by comparing and analyzing the test results of the system and the simulation results of icing prediction model,the accuracy of icing prediction model is preliminarily verified.By comparing the test results of indoor simulation icing test system and the simulation results of pavement icing model,the influencing factors of asphalt pavement icing are deeply analyzed.The results show that when other factors remain unchanged,the icing time gradually increases with the increase of ambient temperature,but the icing rate decreases,and the icing time required to increase the same temperature becomes longer.With the increase of wind speed,the icing time decreases gradually,and the icing rate increases,and the icing time required to reduce the same temperature becomes shorter.With the increase of ponding depth,the icing time gradually increases,and the icing rate first increases and then decreases.The icing time required for the increase of ponding depth at the same height first decreases and then increases.Based on the on-site temperature observation and monitoring data in Kangding area,the temperature field of steel bridge section and subgrade section between tunnels in seasonal freezing area is analyzed by general finite element analysis software.The results show that the span has no effect on the temperature field of the surface of each structural layer of the steel bridge section between tunnels,and different factors have similar effects on the temperature field of the surface of each structural layer of the steel bridge section between tunnels and subgrade section.The larger the wind speed is,the greater the temperature change range is,but the temperature change rate decreases gradually with the increase of wind speed.The amplitude of air temperature with radiation is higher than that without radiation;In the time before the start of sunshine,the temperature change of the surface of each structural layer when considering radiation is the same,but the influence degree of subgrade section is obviously greater than that of steel bridge section.In the time affected by sunshine,the longer the sunshine time,the greater the temperature amplitude.When the sunshine time is 6h,the maximum surface temperature of steel bridge section increased by7.87℃ and that of subgrade section increased by 6.1℃ compared with that without considering radiation.When the sunshine time is 12 h,the maximum surface temperature of steel bridge section increases by 9.83℃ and that of subgrade section increases by 7.63℃compared with that without considering radiation.The minimum temperature at the road surface of the steel bridge section is 0.44℃ lower than that of the subgrade section,which is more prone to icing.Based on the phase change heat transfer equation,water migration equation and stress-strain control equation,through the secondary development of general finite element analysis software,the icing prediction model of steel bridge section between tunnels in seasonal freezing area and the thermal-hydro-mechanical coupling model of subgrade section in saturated state are constructed.The results show that when the wind speed is 2m/s,the water film in the steel bridge section between tunnels has completely frozen at about h =0.5h,and has remained frozen since then.When the wind speed is 0.5m/s,the water film completely freezes at about h =5h,and there is an obvious melting trend at about h =14h.The ice content of the upper layer of the subgrade section between tunnels is the most,and shows the change law opposite to the temperature;The maximum stress on the road surface is 363 kpa,and the maximum vertical displacement when considering the frost heaving of soil foundation is 3.12 mm.