Study On Mechanical Properties Of Lime And Ash Modified Subgrade Silty Soil In Seasonally Frozen Area

Seasonal frozen soil areas in China are widely distributed.The compacted subgrade soil in the seasonal frozen area is subjected to repeated freeze-thaw cycles.The macroscopic mechanical behavior of the subgrade soil changes in this environment to varying degrees,resulting in bulging,turning,and freezing.Common diseases such as swelling and sinking.The silty soil in Jilin Province is widespread,and the soil itself has a loose structure and is significantly affected by freeze-thaw cycles.Therefore,this paper selects the silty sand of Songyuan for improvement test,which has practical engineering significance for the silty sand for roadbed.At present,the engineering community has used lime to improve silt soil based on engineering construction experience and the effect is remarkable.In order to provide a better theoretical and experimental reference for the practice of lime-modified silt soil engineering,this paper uses a combination of laboratory tests,theoretical analysis,and finite element software simulation analysis to focus on the study of lime-modified silt soil under the action of freeze-thaw cycles.The static characteristics and its changing trend,the static characteristics and the changing trend of the lime-sand ash improved silt soil,and the ANSYS finite element software was used to simulate the change of the safety coefficient of the soil subgrade slope before and after the freeze-thaw cycle and before and after the improvement The improvement of soil under the action of freeze-thaw cycles.The main contents are:firstly,under the optimum moisture content of each lime content,the static triaxial test is carried out on the silt soil compaction specimens with different freezing and thawing cycles,through the cohesion,internal friction angle and shear strength Analysis,the optimal amount of lime is obtained;then on the basis of this,furthermixing with fly ash is further improved,and under the optimal moisture content of each lime-ash ratio,the silty sand compacted with different freezing and thawing cycles Conduct a static triaxial test,and then research and analyze the cohesion,internal friction angle and shear strength to find the best ratio of lime-lime-reinforced silty soil;finally,the ANSYS finite element software is used to study the subgrade slope before freezing and thawing The stability of plain soil,lime-modified soil and lime-lime-improved soil slope under different conditions and the stability of plain soil,lime-improved soil and lime-lime-improved soil under different freezing and thawing cycles,that is,the stability of improved subgrade soil to slope Influence and the effect of freeze-thaw cycles on slope stability.The results show that: compared with plain soil,the silty soil improved by lime or lime has obvious improvement in many aspects,including cohesion,internal friction angle and shear strength;but cohesion,internal friction angle and There is no obvious relationship between the change of shear strength and the number of freeze-thaw cycles;when lime is used,the cohesion and shear strength of lime-modified silty soil increase first and then decrease with the increase of lime content.The trend is that the content of lime reaches the peak when it is 6% ～ 8%.After comprehensive consideration,6% is selected as the best content;in the lime sand modified limestone,under the same number of freeze-thaw cycles,the cohesion and shear resistance The strength increases with the increase of the fly ash content in the soil;the addition of fly ash has little effect on the internal friction angle of lime-modified silt,and the internal friction angle of lime-lime-modified silt is more than that of plain soil In terms of,there is also a substantial improvement;based on the analysis of ANSYS finite element software,the slope stability coefficient is analyzed.Compared with plainsoil,the soil of the subgrade slope is stabilized by lime-modified silt soil and lime-lime-modified silt soil.