Experimental Study On The Characteristics Of Cement Modified Loess Subgrade Filler For Baoji-Lanzhou Passenger Dedicated Line

As the research background of baoji to lanzhou high speed railway passenger line,using the method of field investigation and indoor test,take undisturbed soil and remolded soil of railway subgrade as the research object.First through the compression test,shear test,consolidation and compression test,comparative study the physical and mechanical characteristics of undisturbed loess,remolded loess and cement modified loess.Then through the test of different freeze-thaw cycles,lucubrate of the original state-remolded-improved loess freeze-thaw conditions and cement content of the three changes in the characteristics and links.The main work of the paper is as follows:(1)Through the reshaping of loess cement after improvement,found to weaken collapsibility and improve stability and frost resistance,plastic limit is higher than before,there will be a linear increase in cement content,original powdery properties of soil changed more inclined to sand.(2)With the increase of cement content,it is very effective for cohesion enhancement,but has little effect on internal friction angle,so the cohesive force is mainly increased to improve the shear strength of the soil.Compressive strength will increase as the cement content increases,and proportional to the number of days of maintenance,in the early stage of maintenance the strength increases greatly,but later strength is mild.(3)As the number of freeze-thaw cycles increases,compressive strength,shear strength and cohesion of undisturbed,remolded,improved loess is markedly weakened.Under the first freeze-thaw cycle strength is the most serious,influence of remolded loess is greater than that of cement modified loess.Higher cement mixture ratio the smaller internal friction angle,compression coefficient and compressive modulus change damage of freezing and thawing is slight.(4)The strength of cement improved loess structure is mainly reflected in the shear strength,by increasing the cement content can increase the structural strength,With the increase of freezing and thawing cycle of soil structural strength and cohesion of close to overlap.Through analysis can make the roadbed under the condition of freeze-thaw to get adequate protection,the best mix proportion of cement is 8%.The results of the study can provide guidance and theoretical help for seasonal frigid engineering construction or similar engineering design.