Experiment And Research Of Mechanical Property Evolvement Rules Of Cement-stabilized Macadam Bed Under Effect Of Long-time Freeze-thaw

This paper takes cement-stabilized macadam of high-speed railway subgrade bed in severe cold areas as the research subject.Indoor experiments were conducted to simulate the change laws of unconfined compressive strength and breaking strength of cement-stabilized macadam bed after experiencing long-time freeze-thaw cycle;MATLAB was adopted to conduct numerical fitting for the strength change laws under the first 50 freeze-thaw cycles;and predictions were made for the unconfined compressive strength and breaking strength after 100 free-thaw cycles.With the above efforts,a reasonable graded cement-stabilized macadam to resist long-term freeze-thaw cycle is finally attained.The followings are major research results:(1)Under the effect of long-time and repeating freeze-thaw,both the compressive and breaking strength of cement-stabilized macadam experience marked change.Cement-stabilized macadam samples of different proportion of the material show significant decrease of compressive and breaking strength after the first 20 freeze-thaw cycles;however,after 20 cycles,these indicators gradually become stable.A greater proportion of cement brings a more significant increase of durability to the sample under freeze-thaw effect;with the same proportion of cement,that of fine-grained soil has little effect on durability under freeze-thaw effect.(2)Long-time freeze-thaw cycle places more effect on breaking strength than compressive strength;thus,breaking-compressive ration of cement-stabilized macadam decreases as the number of freeze-thaw cycles increases,and its anti-cracking ability becomes worse at the same time.(3)Five fitting models are adopted to conduct numerical fitting of the change laws of compressive and breaking strength of cement-stabilized macadam of different proportioning against the number of freeze-thaw cycles.After comparing the fitting models,the paper finds that MMF model is applied to the fitting and prediction of the relationship between compressive strength of cement-stabilized macadam and the number of freeze-thaw cycles.(4)It is suggested to sieve granules with a diameter less than 0.1 mm out and add 3% of cement to cement-stabilized macadam as the reasonable graded cement-stabilized macadam to resist long-term freeze-thaw cycle.The above suggestion is gained according to the change laws of the compressive and breaking strength of cement-stabilized macadam under long-time freeze-thaw effect against the number of freeze-thaw cycles,and based on the strength prediction of the results of curve fitting after 100 times' freeze-thaw cycles.