Study On Health Status Evaluation And Prevention Of Roadbed Freezing Damage Naqu-yangbajan Section Of National Highway 109

Naqu region in Tibet is a typical seasonal frozen soil region with high altitude and high cold because of its harsh climate,high altitude,long duration of low temperature,large temperature difference between day and night and between seasons,and sensitive ecological environment.In this area,Subgrade Frost damage occurs frequently,which seriously affects the normal operation of the road and regional economic development.In recent years,scholars at home and abroad have made a lot of achievements in the research of Highway Subgrade Frost damage in seasonal frozen area.However,due to the influence of climate,environment,geological conditions,freeze-thaw cycle and other factors,the problem of Highway Subgrade Frost damage in deep seasonal frozen area is still prominent.Therefore,it is necessary to deeply study the freezing damage of Naqu area in Tibet,and put forward the corresponding prevention and control suggestions of subgrade freezing damage.Based on the reconstruction and expansion project of Naqu-Yangbajing section of national highway 109,through field monitoring,indoor freeze-thaw test and theoretical analysis,this paper makes an in-depth study on the freezing damage development characteristics,development law,freezing damage mechanism and influencing factors of this section.Then,the test results are analyzed,and the index factors affecting the Subgrade Frost damage are put forward.The frost damage zoning of Naqu-Yangbajing section of national highway 109 is carried out by using the analytic hierarchy process.The main research work and achievements are as follows(1)Investigate the geological conditions along the supporting project,study the material composition and physical properties of subgrade fillings through indoor geotechnical tests,and analyze the types,mechanism,development characteristics and influencing factors of subgrade freezing damage in seasonal freezing zone.(2)By embedding frost heave meter,temperature and humidity sensor and other components,the freezing damage of subgrade soil was monitored for 18 months,and the change rule of temperature,water content and frost heave amount of subgrade soil in a complete freezethaw cycle was obtained.(3)Indoor freeze-thaw test was carried out,and the variation rule of freeze-thaw deformation with time was obtained.Then,the influence of fine particle content,water content and temperature control on the freeze-thaw deformation was studied,and the indoor freezethaw deformation rule of subgrade soil under different initial conditions was obtained.(4)based on the experiment results and analyses the effect of subgrade frost damage investigation,puts forward the eight indexes of greater influence on the subgrade frost damage,using the analytic hierarchy process was carried out on the road frost damage degree zoning and make health status evaluation,finally on the basis of subgrade frost damage degree can be divided into cold injury of the high rock,rock and low rock.(5)According to the above research on the development characteristics of subgrade freezing damage in seasonal freezing zone,the corresponding principles and measures of subgrade freezing damage prevention and control are put forward.