Study On Micromechanical Properties And Layer Optimization Of Semi-flexible Pavement Material

In this paper,based on the survey of the semi-flexible trial road in Yancheng,the main failure mode of the semi-flexible pavement is found to crack.There are two main types of cracks: surface micro cracks and transverse through cracks.The mesoscopic model of the semiflexible pavement composite trabecular specimen is established by digital image processing technology to characterize the cracking characteristics and the development law of the semiflexible pavement.Considering that the semi-flexible pavement composite material has a double grid structure of cement paste-asphalt mortar,and asphalt mortar-coarse aggregate,the cohesion behavior of asphalt mortar is simulated by the cohesive contact model of CZM.According to the interface damage calculation results of different bonding modes in the same working condition,it is concluded that the interface damage of the matrix asphalt mixture of semi-flexible composite material is earlier than the cement mortar and asphalt mortar after the grouting.Therefore,the flexural ability of the matrix asphalt mixture should be tested for the preparation of the semi-flexible composite material.On the basis of failure mode as tensile cracking,firstly,this paper constructs a threedimensional pavement structure model to analyze the semi-flexible composite material and asphalt concrete.The results of finite element calculation show that the semi-flexible composite material is suitable for the upper and middle surface layers of the pavement structure and is not suitable for as a top,nor bottom layer.Then the mechanical response of the pavement structure under the action of vehicle load and temperature gradient is calculated according to the selection of the suitable layer of the semi-flexible material,and the sensitivity analysis of the material parameters of the surface layer is carried out.The results show that when the semi flexible layer is used as the upper layer,the thickness should not be less than 6cm,and the modulus should be controlled at about 4000 MPa.The total thickness of the semi flexible pavement surface is more than 12 cm,so as to prevent the upper surface of the base from cracking due to excessive temperature stress.Secondly,the regression formula of multiple parameter regression is used to get the regression formula of load stress and temperature stress of semi-flexible pavement,and the fatigue stress formula of semi-flexible pavement is put forward in consideration of the fatigue properties of material.Finally,based on layer optimization,the recommended surface structure of semi-flexible pavement combined with project is proposed.The test section was in good condition during the service period and there was no serious damage.To sum up,this paper analyzes the cracking characteristics of semi flexible pavement on the basis of the characteristics of the semi flexible pavement structure.Based on the semi flexible pavement structure model,the mechanical response of pavement structure and the formula of fatigue stress regression are analyzed,and typical semi flexible pavement structures which are suitable for different vehicle flow is presented to provide a certain reference for use in the future.