Research On The Foundation Characteristics Frost Heaving In Northwest Saline Soil Area And Its Effect On The Deformation Of The Roadbed

In recent years,with the rapid development of Western China Development and traffic construction,the number of highways passing through the salted soil areas of western China has gradually increased.Especially in the seasonal frozen area of northwest China,the frost heave of saline soil has a serious effect on the stability and safety of the roadbed.LiuyuanDunhuang Expressway is another convenient fast-track which is used to go in and out of Dunhuang City.The left section of it is reconstructed based on the existing road,and the waterproofing effect of the lower part of the roadbed is bad;while the right is a new road,and the waterproofing measures under the subgrade are complete.Since the left-section road is in the upper reaches of the Shule River,and the seasonal ecological water of it penetrates from left-section to right-section in the form of seepage every year,it makes the water content of the foundation and the lower part of the subgrade of the left-hand road larger.Meanwhile,because it’s located in the seasonal frost area,the reduction of temperature in winter will cause the frost heave and other diseases to foundation and subgrade,affecting the safety and comfort of driving.In this paper,the relative severe section with frost heaving damage of the left-section road of Liuyuan-Dunhuang Expressway is selected as the research object,and the foundation characteristics frost heave of this section and its effect on the deformation of the roadbed are studied through site monitoring,experiment research and numerical analysis.The main research contents are as follows:(1)The severe sections with frost heaving damage of Liuyuan-Dunhuang Expressway were investigated and analyzed,including geological hydrology,climatic conditions and the form of frost heaving and frost damage.Combined with the specific situation of seasonal ecological water discharge in the Shule River,the main causes of frost heaving damage in this section were analyzed.In addition,a representative roadbed section was selected to arrange the settlement observation point combined with actual condition on site for monitoring the frost heaving deformation of the foundation and roadbed during the one-year frost heaving period.(2)Carry out the corresponding soil test by selecting the subsoil in this section,and analyze and test the composition and moisture content of the soil sample.Specifically,the particle gradation test,moisture content test,compaction test and determination of soluble salts,and the particle gradation composition of soil sample,the moisture content and maximum dry density of original soil,as well as the content of soluble salt were tested,providing the basic parameters for frost heaving experiment of soil sample.(3)The frost heaving test of the foundation soil sample in this section was carried out.The experimental factors affecting frost heave were first identified,and the test parameters of each factor were analyzed and determined.On this basis,the change law of the frost heaving ration of soil sample was analyzed under different compactness,moisture content,salt content and temperature,and the influence law of each factor on frost heave ration was also analyzed.(4)Numerical analysis was carried out on the comprehensive effect of the interaction of foundation and roadbed.Firstly,the theoretical basis of temperature field,deformation field and other models was studied,and the combined effect of temperature field,moisture field,salt field and deformation field were analyzed according to the actual situation.The frost-heave amount of the foundation and subgrade obtained by the comprehensive effect analysis of the deformation field was compared with that measured combined with actual condition.