Research On Application Of Lime-Soil Frozen-thaw Tests

Lime has been widely used in building foundation treatment.Adding lime subgrade to improve the foundation bearing capacity,and both the frost resistance and water imbibition characteristics have been greatly improved.The price of lime is low and economic.Because the application is easy and convenient and the water content of soil base can be quickly reduced,lime soil has been widely used in road subgrade for soil improvement.The cold frozen regions in China are mainly distributed in Heilongjiang,Jilin,Liaoning,Inner Mongolia,QingHai,NingXia and o ther provinces,the size of seasonal frozen soil region of the cou ntry is about 53.5%.Freezing line changes greatly ranged from south to north.The fact of subgrade freeze-thaw cycle effect mu st be taken into account in northeast China during building road s,Highway foundation soil are bound to experience the process of frost-heaving and thawing-settlement indoor test.The physicaland mechanical properties of lime treatment subgrade soil resea rch also is not very good under the action of freeze-thaw,especia lly the micro-aspect.In this paper,on the basis of existing resear ch,relying on the jilin province transportation science and accordi ng to technology plan projects ‘A wet earth Road foundation tre atment technology research(2011103)',conducting indoor physica l and mechanical properties test under different lime content of subgrade soil,and observing its internal microstructure change.Th e research results and conclusion listed below:(1)In the subgrade soil mixed with different amount of lime,the determination of the basic physical indicators(liquid plastic limit determination,optimum moisture content,maximum dry density,specific gravity test and grain size analysis).When the lime dosage increase,the plastic limit rised and the plasticity index decreased,but the liquid limit is basic stability.The optimum moisture content increased after mixed with lime and the maximum dry density becomes smaller.The density of pure lime is important than the soil.soil density increased after adding lime.Because there is chemical reaction between lime and soil particles,the powder clay of the lime treatment been declined.(2)Based indoor basic mechanics test on two kinds of degree of compaction of lime treatment soil to determine the strength change rule of the lime treatment soil under the different dosage of lime and different freezing and thawing times.The test results are below: the unconfined compressive strength is proportional relationship with mixing lime dosage and inversely proportional with the number of freezing and thawing times.CBR test results is that the swell increment and water regain are declined with the increase of the dosage of lime and the swell increment reduced after freeze-thaw teset,and water regain increased.Static triaxial compression test can be concluded that shear strength,and indicating with the increase of the ratio of lime,both the shear strength and cohesion are increased.The freeze-thaw cycle effect decreased shear strength and cohesion.But the internal friction Angle of soil was increased after the first decreases with Lime dosage,and the influence of freezing and thawing times is make internal friction Angle increases.(3)Using scanning electron micro-scope and IPP software to observe soil microstructure.Quantitative evaluation of soil microscopic structure.The results display below: Soil particle and pore were no directionality.Under the action of freezing and thawing the directionality of soil and soil particle of 3% lime content have improved.The direction angle of pore volume is majority on both sides and evenly distributed in the middle.With the increase of the dosage of lime the circular degree of soil particle and pore volume is reduced.Under the action of freezing and thawing soil particle roundness rise,pore volume roundness decrease.Abundance of soil particles is smaller in the process of freezing thawing.Particle shape to be a more oval,elongated.Adding lime to subgrade soil fractal dimension of the soil particles and the pore is reduced.Fractal dimension is reduced in the process of freezing thawing.