Research On Strength And Fatigue Damage Characteristics Of Cement Stabilized Crushed Stone Based On Bimodularity Theory

The present asphalt pavement design method was analyzed and calculated by the elastic layer system theory.It was assumed that all layers were continuous,homogeneous,isotropic,and the displacement and deformation were small.However,in the actual stress of semi-rigid base asphalt pavement structure,tensile stress zone and compressive stress zone were generally existed in the same time.The strength and modulus of cement stabilized materials were closely related to the experimental conditions and the stress state,and the properties of the different tensile and compressive modulus were shown.Whether it was the mechanical properties of cement stabilized materials,or the mechanical response of semi-rigid base asphalt pavement structure,cement stabilized crushed stone base materials had shown the characteristics of difference of modulus of tension and compression,The current design method simply used the compressive resilient modulus as the semi rigid material parameters of asphalt pavement,which would lead to a large error in the design of the thickness and the calculation results of the stress and strain.Therefore,it is necessary to carry out the research of the characteristics of the strength and the fatigue damage of cement stabilized crushed stone considering the difference of tension and compression modulus.Based on the theory that the tensile and the compressive modulus of the curved beam was different,the calculation formula of the bending strength under the conditions which considered the difference of the tensile and the compressive modulus was derived.The flexural strength test,direct tensile strength test and indirect tensile strength test of cement stabilized crushed stone under different loading rates were carried out.The result show that the bending strength was decreased by 20% compared with that without considering the difference of tension and compression.The strength increased with the increase of loading rate under the mode of different loading,which could be approximately expressed as a power function relationship with loading rate.Under the condition of the same loading rate,the strength of the cement stabilized crushed stones under different loading modes was in turn to be the flexural strength >direct tensile strength > splitting strength.The calculation formula of the tensile and the compressive modulus under the conditions which considered the difference of the tensile and the compressive modulus was derived.The four point bending fatigue tests under different stress ratio were carried out,and the flexural fatigue equations of cement stabilized macadam were built.The corresponding tensile and compressive strain was texted on the surface of the curved beam.The growth rule of the tensile and the compressive strain and the decay law of dynamic tensile and compressive modulus in the process of bending fatigue were revealed.The position of the neutral plane of the bending beam was gradually moving upward with the increase of The fatigue test load times.The analytical solution of fatigue damage of four-point bending rectangular section beam was derived.The estimated formula of fatigue life was derived.According to the damage variable defined by the dynamic tensile modulus,the bending fatigue damage model of cement stabilized crushed stone based on the dynamic tensile modulus was establishedThe research results have an important significance to solve the problem of determining parameters of pavement materials the same time has the reference value for the design theory and calculation method of asphalt pavement considering different modulus of tension and compression.