Study On Freeze-thaw Cycles Of Subgrade In Seasonally Frozen Soil Region Of West Sichuan Plateau

With the development of western China and the construction of infrastructure along Belt and Road,the cold region engineering is developing rapidly,and the frozen soil and freezing damage prevention technology has become one of the research hotspots at present.At present,many achievements have been made in the theoretical research and disposal measures of permafrost in China,but there are few researches on seasonal permafrost and less on the subgrade of seasonal per mafrost in western Sichuan Plateau.Therefore,based on field investigation and field test,a series of indoor geotechnical experiments,model tests,numerical simulation and theoretical analysis have been carried out in this paper,taking No.318 National highway in Xinduqiao area of Kangding as the research object.The model design is mainly based on the existing meteorological data and generalizes the experimental model,carries on the field inspection and field test,obtains the relevant material paramet er and configures the test material through the indoor geotechnical test.Through collecting and consulting a large number of documents about model test of frozen soil roadbed at home and abroad,the model is designed and made.Model test in order to study and adopt two models(one of which has soil resistance wire),the indoor model test is carried out simultaneously.Through the control of test conditions,several freeze-thaw cycle tests of roadbed model are designed,and the temperature field is obtained.The variation law and relation of water field and deformation field are analyzed.The influence of water heat effect on deformation under freeze-thaw cycle is analyzed,and the mechanism of freeze-thaw cycle effect of seasonal frozen subgrade under freeze-thaw cycle is explained.On the basis of the three-field coupling equations of water and heat,the mathematical model is established,and the numerical analysis of the roadbed of G318 National highway in Xindu Bridge area of Kangding is carried out by using the numerical analysis software,and the model test is verified numerically.By comparing the results of model test and numerical simulation,it is found that the two results are in good agreement with each other.Through the work of model design,model test and numerical simulation,the freeze-thaw cycle effect of subgrade in seasonal frozen soil region of western Sichuan Plateau is studied.The results can provide theoretical reference and experimental basis for the prevention and treatment of roadbed frost damage in this area.