Study On Damage Of Cement Stabilized Macadam Based On CT Images

Cement stabilized macadam material is a pavement base material widely used in China.Based on the CT images of cement stabilized macadam material damage,this paper establishes the indicators of cement stabilized macadam damage and constructs a statistical damage constitutive model of cement stabilized macadam under uniaxial compression.First,the CT scanning technology is used to obtain the CT image of the mesostructure of the cement stabilized macadam material after loading.Through the CT image feature analysis and image processing of two typical structures of cement stabilized macadam,the distribution of cracks in the two typical structures is obtained:the cracks of the N1 structure cement stabilized macadam are distributed evenly across the entire section,and the N4 structure cement stabilized macadam Most of the cracks in the specimen showed a ring-shaped development,and the cracks mainly developed along the interface between the aggregate and the mortar.Secondly,based on the theory of grayscale image co-occurrence matrix,a movable grayscale index was established to characterize the damage of cement stabilized macadam material by P_sgl.The calculation results of P_sglgl of CT images of two typical structural cement stabilized macadam materials show that the P_sglgl value of the section first increases and then decreases with the increase of load,which can well represent the damage development process of cement stabilized macadam materials.The damage and load of cement stabilized macadam materials show a second increasing trend,and the damage development process accounts for about 80%of the entire loading process.In the early stage of loading,the damage development rate of N1 structure and N4structure is equal.In the middle and late loading,the damage development rate of N1structure is higher than that of N4 structure.Finally,based on the statistical damage theory and the correlation between changes in P_sglgl and damage development,P_sglgl was introduced into the damage variable,and a statistical damage constitutive model for cement-stabilized macadam material under uniaxial compression was constructed.By comparing the calculation results of the model and the loading experiment results,it can be shown that the calculation results are basically consistent with the experimental results.There is a certain difference between the mechanical properties of the two structures,and the model calculated limit stress and failure point stress errors are small,which can reflect their mechanical properties.The uniaxial compression statistical damage constitutive model of cement stabilized macadam material constructed in this paper can better reflect the mechanical characteristics of cement stabilized macadam material under load.It is useful for studying the internal damage development process and load of cement stabilized macadam material.The influence of mechanical properties is of great significance to control the cracks of cement stabilized macadam base and improve road performance.