Strength Characteristic Study On Cement And Asphalt Stabilized Macadam Of High Speed Railway In Cold Areas

The length of high-speed railways in cold areas is increasing with the rapid development of high-speed railway construction in China.However,the problem of the freezing thawing settlement in the cold areas seriously affects the driving safety,and the mismatch of the strength and stiffness of the base bed affects the driving comfort.Address this issue,this paper focuses on the study of cement stabilized macadam packing in subgrade bed surface.Through laboratory experiments,study the effects of particle grading,cement content and emulsified asphalt content on unconfined compressive strength,flexural strength,dry shrinkage performance and properties of materials after freezing-thawing cycle.Based on the comprehensive analysis,the reasonable ratio of high railway subgrade bed surface packing in cold areas was put forward.The main findings are as follows:(1)The influence of fine particle content on unconfined compressive strength under different sample size and curing age was studied through experiment.it was founded that the fine content of cement stabilized macadam has less influence on unconfined compressive strength.In order to improve the permeability of the surface layer of the base bed,it is feasible to remove the open-graded cement-stabilized gravel with the particle size less than 0.25 mm.(2)The size of the unconfined compressive strength experiment mold of coarse grained soil is designed by itself.The experiment tube wall is composed of two parts.The detachable structure is conducive to sample demoulding.And the large size experiment mold can better reflect the unconfined compressive strength of coarse soil.(3)Based on the removal of particle gradation with particle size less than 0.25 mm,adding cement can improve the unconfined compressive strength,flexural strength and frost resistance of the sample,but also increase the dry shrinkage.Adding emulsified asphalt can effectively reduce the dry shrinkage,improve the flexibility,increase the ability to resist deformation,and the frost resistance is also improved again.Under the condition of strength and dry shrinkage,it is advisable to use emulsified asphalt cement stabilized macadam with the removal of fine particles less than 0.25 mm and the addition of 5% cement and 2% emulsified asphalt.(4)The strength of emulsified asphalt material is formed slowly,but with the increase of curing age,the strength of emulsified asphalt cement stabilized macadam has been significantly improved,and the frost resistance has also exceeded that of cement stabilized macadam material.