Mechanical Properties Of Cement Stabilized Crushed Stone With Rubber Powder Experimental Study On Frost Heave And Thaw Settlement

China is a big country of frozen soil,and the seasonal frozen soil area accounts for 53.5 % of the national area.With the rapid development of high-speed railway construction,the construction mileage of high-speed railway in this area is increasing day by day.By optimizing the performance of the surface material of the subgrade,it is urgent to alleviate the frost heaving and thawing diseases of the subgrade.In this thesis,the cement stabilized macadam filler on the surface of the subgrade bed is taken as the research object.The equal volume replacement method is used to replace the fine aggregate below 1.7 mm with rubber powder,and the fine particles below 0.1 mm are removed.The rubber powder replacement level is used as a variable to prepare a rubber powder cement stabilized macadam.The indoor unconfined compressive strength test,freeze-thaw cycle test,CT scanning test and frost heave and thaw settlement test were carried out to explore the anti-frost heave mechanical properties of the surface filler of rubber powder cement stabilized gravel bed.The main results are as follows:(1)The study of the influence of rubber powder cement stabilized macadam on the unconfined compressive strength under varying rubber powder content and 7d curing age was conducted through an indoor unconfined compressive strength test.It was discovered that the unconfined compressive strength of the cement stabilized macadam decreased as rubber powder replacement increased.When the replacement amount of rubber powder is 45 %,the average 7d unconfined compressive strength of the material is 1.35 MPa,which still meets the basic requirements of the strength of railway subgrade bed filler.(2)The unconfined compressive strength data of 28 d and after five freeze-thaw cycles was investigated through the amalgamation of an indoor unconfined compressive strength test and a freeze-thaw cycle test.The frost resistance and mechanical characteristics evolution of cement stabilized macadam combined with rubber powder were examined and examined.The frost resistance evaluation index BDR initially declined,but then rose with the augmentation of rubber powder.When the rubber powder was abundant,the cement-stabilized macadam blended with rubber powder demonstrated superior freeze-thaw resilience.The Duncan-Chang hyperbolic model enabled the formulation of the material’s parameter fitting equation,introducing the strain softening adjustment coefficient to more accurately depict the nonlinear mechanical properties of the rubber powder cement stabilized gravel process.At the same time,after analyzing the stiffness parameters of the material,it is found that the addition of rubber powder significantly improves the toughness of the material compared with the traditional cement stabilized gravel material.(3)A microscopic analysis of industrial CT scanning and freeze-thaw cycle tests reveals distribution of rubber powder in cement stabilized macadam material,and further elucidates the micro-pore expansion and evolution law of cement stabilized macadam material under various rubber powder content over the freezethaw cycle.The internal mechanism of freeze-thaw damage of the material is clarified by the porosity expansion process.A close correlation exists between the sample’s porosity augmentation rate and the amount of rubber powder.When the content is high,the internal rubber powder of the sample can obviously alleviate the freeze-thaw damage caused by frost heaving force,which shows a lower porosity amplification rate and better frost resistance.(4)The frost heave and thaw settlement test device was developed.Through the frost heave and thaw settlement test of graded gravel and cement stabilized gravel filler,the influence of cement and rubber powder on the frost heave and thaw settlement of the sample was clarified.The results show that the addition of rubber powder and cement is the key factor affecting the frost heave displacement of the sample,and the frost heave displacement decreases with the increase of rubber powder and cement content.Under the condition of water supplement and unidirectional freezing,when the replacement amount of undoped rubber powder and rubber powder is 30 %,the maximum frost heave displacement of graded gravel filler is 2.53 mm and 0.37 mm respectively,and the reduction rate of frost heave displacement is 85 %.The maximum frost heave displacement of cement stabilized gravel filler is 0.63 mm and 0.31 mm respectively,and the frost heave displacement reduction rate is 51 %.Considering the mechanical characteristics,frost resistance and deformation law of frost heave and thaw settlement of cement stabilized macadam samples mixed with rubber powder,it is considered that the addition of rubber powder improves the frost resistance and toughness of cement stabilized macadam material on the surface of subgrade bed while satisfying certain strength,and reduces the deformation of frost heave and thaw settlement.When the volume of rubber powder is replaced by30 % of particle size aggregate below 1.7 mm,the parameters are optimal.