Study On The Difference And Prevention Of Highway Subgrade With Sunny-Shady Slopes In Seasonal Frozen Soil Regions

With the continuous expansion of highway construction to high latitude and highaltitude mountain areas,there are a large number of seasonal frozen soil along the highway in Altay Prefecture,Xinjiang.Due to the different directions of the subgrade along the highway,the highway subgrade works in the region have negative and positive slope effects,and the temperature and frost heave deformation on both sides of the subgrade slope are significantly different,resulting in the subgrade tilting A series of engineering diseases such as longitudinal cracks and uneven frost heave pose a serious threat to the safe operation of local highway engineering.In order to control the diseases of highway subgrade engineering in seasonal frozen soil areas,it is important to study the thermal effect mechanism of shady and sunny slopes and relevant prevention and control measures.This thesis relies on the G331 Qinghe-Altay Highway Construction Project,selects typical roadbed section measurement data,and through numerical simulation,obtains the seasonal freeze-thaw characteristics,freezing depth,temperature field distribution,and differential development process of frost heave deformation of the roadbed under different directions.Furthermore,it explores the prevention and control measures for the shady and sunny slopes of the roadbed in seasonal frozen soil areas.To provide scientific basis for the future construction and maintenance of highways.The main research content and results are as follows:1.This thesis superimposes meteorological conditions such as solar radiation,temperature,wind speed,and evaporation heat consumption into the second and third types of boundary conditions,and establishes a coupled finite element analysis model for roadbed thermal analysis to study the temperature and displacement of roadbed in seasonally frozen soil areas.2.The different orientations in the Altay region have a significant impact on the synchronicity of the freeze-thaw process of permafrost roadbed,with the east-west trend having the greatest time difference in the freeze-thaw process of the shoulders of the lower sunny-shady slope,and the north-south trend having basically synchronized freeze-thaw processes of the shoulders of the lower sunny-shady slope.During the freezing process,the shoulder on the shady slope enters the freezing state earlier than the shoulder on the sunny slope for up to 15 days,and the freeze-thaw period on the shady slope is longer than that on the sunny slope.The maximum freezing depths of the shoulder on the shady slope in the east-west,northeast,and north-south directions are 2.8m,2.6m,and 2.2m,respectively.The difference in freezing development time and the maximum freezing depth pattern in the three directions are: east-west direction>northeast direction>north-south direction.3.Correspondingly to the temperature pattern of the shoulder on the shady slope,the deformation difference of the roadbed in the month with the highest vertical displacement difference is arranged from large to small in three directions: east-west direction>northeast direction>north-south direction.There is a significant asymmetry in the vertical displacement distribution of the shoulder on the shady and sunny slopes of the local roadbed.During the freezing process,the vertical displacement difference of the frozen soil roadbed is the largest in March,The deformation difference of the roadbed is arranged from large to small in the month when the vertical displacement difference is the largest: east-west direction>northeast direction>north-south direction.4.In In view of the negative and positive slope effect of seasonal frozen soil subgrade,the compound prevention and control measures of thermal insulation berm+thermal insulation board+block stone layer are proposed,and the non isothermal seepage model simulation calculation is established through the heat transfer theory of Porous medium.The calculation results show that the composite prevention and control measures of insulation berm,insulation board,and block stone layer can effectively control the frost heave displacement of the roadbed.Especially compared with traditional prevention and control measures for permafrost roadbed,it has a significant effect on suppressing the difference in frost heave displacement and the difference in frost heave development time on both sides of the roadbed under the effect of sunny and shady slopes.