Research On Dynamic Behavior And Structure Optimization For Typical Asphalt Pavement

Asphalt pavement, which is the major structure for high-grade pavement in China, plays a decisive role in the development of highway traffic. However, the contradiction between the increasing requirement of high-speed and heavy-load transportation and the lack of pavement service life has become the bottleneck in highway development. One of the important reasons is that the actual stress state is hard to be assessed through static design method used in our country currently. Therefore, many pavement diseases are difficult to be explained properly. Consequently, a prerequisite for reasonably analyzing pavement damage mechanism, optimizing structure of asphalt pavement, and improving pavement service life is to understand the dynamic behavior characteristics for different types of asphalt pavement structure. In this dissertation, firstly the latest research progress about the design method of asphalt pavement, the theory of pavement dynamics and experimental investigations was comprehensively reviewed. Then, based on the characteristics of asphalt pavement structure and engineering environment in our country, asphalt pavement with semi-rigid base (SI), inverted asphalt pavement structure (S2), and compound asphalt pavement (S3) were selected to analyze the dynamic behavior for typical asphalt pavement structures. The research presents a systematic work on the dynamic modulus of pavement materials, the law of real response under dynamic load and the structural behavior through numerical technology. The major research results are summarized as follow:Firstly, by the literature review and data research, the dynamic properties of pavement materials such as subgrade soil, graded gravel, inorganic binders stabilized aggregate and asphalt mixture, were analyzed from the constitutive relationship, empirical prediction model, parameter value domain etc. The change laws of the dynamic modulus and phase angle were obtained through single-axle compressive dynamic modulus test which chose SMA-13, AC-20, and AC-25 as research materials. By analyzing the master curves of dynamic modulus and time-temperature shifted factor, the sensibilities of visco-elastic material towards load frequency and environmental temperature was comment, and the dynamic modulus values in specific conditions were expanded to more extensive time-temperature space.Secondly, through the vehicle load test which chose the dynamic strain as evaluation parameter, the real response characteristics of three typical asphalt pavements were obtained, and the influence of pavement structure, vehicle load type, speed, axle type, tire pressure and environmental conditions on dynamic strain were also evaluated. The significance of influencing factors such as the pavement temperature, vehicle load, speed and their coupling influence were obtained through interactive orthogonal experiment. Furthermore, with the highly significant factors as independent variables, the prediction models for dynamic strain at the bottom of asphalt surface that can meet the demand for engineering analysis were established. The fatigue lives of asphalt layer in different pavement were studied comparatively based on the dynamic strain data measured on site.Thirdly, through FWD test, measurements of surface deflection and strain response were mutually combined to examine the properties of dynamic deflection basin and actual strain response in typical asphalt pavement structures. According to multiple regression analysis on the basis of the strain response and pavement temperature on site, the temperature modified coefficients of strain response for three typical asphalt pavement were determined respectively. So that it could make transformation between the dynamic strains in measured and standard temperature conditions. The corresponding relation between FWD load and vehicle load was also studied on the basis of strain equivalence. Thus, the linear regression equations were derived from the corresponding relation between FWD loads and vehicle load with standard axle load. The correlation between dynamic strain and dynamic deflection basin parameters was studied using the gray relation entropy analysis method. Hence, prediction models of asphalt pavement strain were established on the basis of dynamic deflection basin parameters. At last, the evaluation method for strain response at the bottom of surface was proposed.Fourthly, according to numerical analysis by means of ABAQUS software, a three-dimensional finite element model in dynamic mode was established, whose rationality was verified based on measured strain response in vehicle load test. During the research, the surface deflection, tension strain at the bottom of asphalt layer, tension stress at the bottom of semi-rigid base, compression strain at the top of subgrade, and shear stress in asphalt layer were taken as the key mechanical parameters. The difference between dynamic and static mechanical behaviors was clarified according to the comparative analysis between dynamic and static response. By analyzing the dynamic response laws of asphalt pavement due to vehicle load parameters such as vehicle axle load, speed, axle type, effect of horizontal load etc, the dynamic behavior characteristics of asphalt pavement were evaluated.Finally, by using numerical simulation method, the research on asphalt pavement structure combination was made, and accordingly the key control indices were presented for different types asphalt pavement. On the basis of correlation analysis, the positive and negative correlation between the pavement structure parameters and dynamic response indices was determined. In order to provide reference for the optimization design of asphalt pavement, the adjustment approaches of structure parameters that could optimize the stress states of pavement structure were proposed based on the results of correlation analysis between the pavement structure parameters and dynamic response indices.