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For ensure the engineering quality of high speed railway in the collapsible loess area, toresearch a convenient and economic feasible foundation treatment method high for collapsibleloess of high speed railway, is one of the main targets of high-speed railway in our country.XiBao passenger dedicated line is located in the collapse of loess area of Guanzhong, studythe engineering properties of foundation soil, it is the theoretical basis to choose collapsibleloess foundation treatment methods for the engineering. In this paper, it is mainly manifestedresearch work in the following aspects:(1)We has carried on the exploration work of foundation soil in QiShan and XingPingtest section of XiBao passenger dedicated line. And we has done the density, water content,liquid limit, plastic limit, compression tests, the compaction and the loess collapsibility tests.Then obtained the basic physical properties and mechanical parameters of foundation soil. Bythe experimental results, the density and the dry density of the cement-soil increase as thedepth increases; After the foundation has been compacted by CFG pile+Hammer ExpansionColumn Pile or Compacted Cement Pile, density, dry density and compression modulus ofthe soil sample increased, water content and initial void ratio reduced; density, Drydensity,density and compression modulus of Sampling from drilling in general have a smallpit income, drilling and the moisture content, the initial void ratio is obtained from trial pitsample is big.(2) It shows that there has good correlation between the coefficient of collapsibility loessand loess density, dry density, void ratio, compression modulus of localized parameters, etc.Through curve fitting, we established a series of correlation data models betweencollapsibility coefficient and localized parameters, it can forecast the collapsibility of loessreliably in theory, and it certain has application value. We have established the regressionequation between the localized parameters and bearing capacity on the basis of the pressuretest.(3)QiShan test section is not gravity collapsibility loess ground and collaspsibilitycollapsibility loess ground, The thickness of the collapsibility loess is4m, its collapsibility loess level is Ⅱ. With column hammer reaming compaction pile and CFG pile afterprocessing, the collapsibility of loess is completely eliminated.XingPing test section area is not gravity collapsibility loess ground and collaspsibilitycollapsibility loess ground, The thickness of the collapsibility loess is10m, its collapsibilityloess level is Ⅲ, after it be treated by cement-soil compaction pile and CFG pile, totalcollapse settlement amount of the foundation soil is reduced, the gravity collaspsibility hasbeen completely eliminated, meet the engineering requirements.
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