Study On Subgrade Stability In Typical Seasonal Frozen Area Of Pingzan Expressway Project

Expressway,as one of the important symbols of a country's development degree,affects the country's economic development to a certain extent.In some regions with special subgrade,such as in northeast China and other seasonal permafrost regions,the treatment technology is not yet mature,and there are still many deficiencies in the technical level.Therefore,it is particularly important to study the stability and settlement deformation of freeze-up expressway.Based on Pingzan expressway project in Shijiazhuang,Hebei province,this paper studies the subgrade stability in typical seasonal freezing zone,and combines theoretical and experimental analysis.The main contents and results of the research are as follows:(1)The site sampling of the packed soil used in the subgrade of the test section was carried out,and the samples were tested by particle analysis,test of limit water content,test of compaction test of bearing ratio,triaxial test,etc.The obtained data were sorted out and analyzed to obtain the corresponding physical and mechanical properties of the samples and judge the rationality of the use of the samples.(2)The frost heaving characteristics of roadbed fill are studied from four aspects.They are the temperature change after freezing,depth of freezing,frost heaving deformation and moisture content after freezing.The main factors leading to frost heave were analyzed,and the changes of mechanical properties of samples after freezing-thawing cycle were summarized.(3)Using Midas GTS NX rock and tunnel structure finite element analysis software for numerical simulation of the subgrade through the model to understand the stress field and displacement field of the whole structure,including the part of the stress concentration and size distribution of displacement.In order to find out the deficiencies and defects of the project,guide the project to design and maintain the structure scientifically and reasonably.(4)Based on the analysis of theory and practice,the main reasons affecting the stability of the roadbed of Pingzan expressway are found out,and according to the actual situation,reasonable protection measures are put forward for the weak links of the roadbed structure.It provides a useful reference for the design theory and construction method of subgrade in typical seasonal frozen area.