Study On The Strength Mechanism Of Lime Soil For Road Use

The Jihuang expressway is located in the seasonal frozen plain area.The groundwater level is greatly influenced by the seasonality.The high quality road building materials along the line are scarce,and the rock and soil which can be used as subgrade filling materials are mainly silty clay.In order to make full use of the silty clay along the line and reduce the destructive exploitation of natural resources,lime improved silty clay is used for roadbed filling.Based on the subject and practical project of the research on the treatment technology of the roadbed of the road over wet soil,the physical and mechanical indexes of the lime soil,the method of measuring the lime content and the mechanism of the strength formation are systematically studied.The following achievements have been obtained.?1?Select the silty clay of Jihuang section to improve the lime treatment.The test results of the physical properties of lime soil show that the liquid limit and plastic limit of the modified soil are all increased and the plastic index decreases.With the increase of the amount of lime,the content of powder and clay decreases,and the specific gravity increases first and then decreases.?2?The test results of the lime soil mechanics index of the Jihuang section showed that with the increase of lime content and the growing age,the unconfined compression strength increased and the increase was first small;with the increase of compactness,the unconfined compressive strength increased;the water absorption and expansion of lime soil decreased greatly with the addition of lime in the soil;with the increase of lime content,the CBR of lime soil was first.The best lime content for subgrade soil is 5⁹%after increasing and decreasing trend.?3?The lime content in lime soil under different conditions is studied.It is concluded that the attenuation of lime dose mainly occurs before 14d,and then gradually becomes stable.As the amount of lime is increased,the reduction of lime is also increased.Compared with the dry soil method and wet soil mixing method,the wet soil method is mixed,the particle size becomes larger,the contact area of lime and soil particles becomes smaller,the reaction of lime and soil is inadequate,and the former is lower than the latter.Compared with the first time mixing method,the two lime mixing method has large attenuation of lime.Two uneven ash can improve the wet soil mixing,the lime and soil increased contact area.With the increase of moisture content,the decrement of lime also increases.When lime content is detected,the moisture content of lime soil should be its corresponding optimum moisture content.According to the titration result,the lime content curve is calculated through the EDTA standard curve.In engineering,the initial lime content can be derived from real-time lime content.?4?The results of the study on the microstructure and mineral composition of lime soil by SEM and XRD show that Ca?OH?₂ crystal is clearly visible in the magnified image of lime soil microstructure.With the increase of lime content,the density of lime soil structure increases first and then decreases.With the increase of compaction degree and age,the structure of lime soil is also more and more compact.With the growth of age,we can see that the Ca?OH?₂ crystal is decreasing gradually,and it is verified that the lime content in EDTA titration decreases gradually.Compared with the mineral composition before and after the improvement,it was found that the Ca?OH?₂ crystal,calcium silicate hydrate?CSH?and calcium aluminate?CAH?were produced in lime soil.