Analytical Solution And Numerical Simulation Of Unsaturated Asphalt Pavement

Asphalt pavement is affected by moisture in the environment,it is mostly in a unsaturated state during service.However,in order to the improve the calculation efficiency,the existing mechanical analysis of the asphalt pavement seepage field mostly simplified the pavement form into a fully saturated or pure elastic state,resulting in a large deviation between analysis results and actual engineering test results,which made the mechanical analysis of asphalt pavement severely disconnected from actual engineering applications.Therefore,in order to solve the problem of moisture damage caused by the vehicle load and moisture coupling effect of the asphalt pavement,the unsaturated state of the asphalt pavement must be taken into consideration.At the same time,in order to obtain the mechanical characteristics of the asphalt pavement under the unsaturated state,we must firstly obtain the true pavement material hydraulic conductivity.However,limited by the test equipment and test methods,the current research has not been able to obtain satisfactory results of the hydraulic conductivity test.Based on the above problems,this paper obtains an accurate material hydraulic conductivity by independently developing a novel multi-directional seepage device.At the same time,it introduces unsaturated porous media theory to carry out analytical solution and numerical simulation analysis of unsaturated asphalt pavement structure to quantify the mechanical properties of moisture on asphalt pavement.Firstly,the theory of unsaturated porous media is introduced to establish the mechanical model and basic control equations of unsaturated asphalt pavement;The integral transformation method in the mechanics of layered elastic theory is used to derive the analytical solution of the single-layer elastic system.After substituting the loading and boundary conditions,the exact solution of the elastic half-space volume is obtained.Secondly,according to the basic governing equation,the single-layer transfer matrix of unsaturated asphalt pavement is obtained.The wave transfer method,that is,the reflection-transmission matrix method,is used to derive the general solution of the elastic system of the multi-layer unsaturated asphalt pavement.The surface state vector is obtained by using the charged carrier vector.Subsequently,the model is degraded to a saturated state,the accuracy of the model is verified,and the numerical calculation program flow is given.Thirdly,the hollow Marshall specimen was used to achieve the separation of the horizontal and vertical seepage of asphalt mixture.Subsequently,the design and development of the test piece forming device,anti-seepage device and multi-directional seepage device were carried out.The AC and OGFC asphalt mixtures were tested for moisture penetration,and the horizontal and vertical hydraulic conductivity at different porosities and hollow diameters were measured.Finally,based on the ABAQUS finite element platform,a three-dimensional model of saturated and unsaturated asphalt pavement under FWD loading is established,and the key mechanical indicators inside the structure are compared and analyzed.The mechanical response of asphalt pavement under unsaturated state is obtained,and the corresponding disease types are pointed out.At the same time,a three-dimensional model of saturated asphalt pavement under moving load is established to analyze the timehistory changes and spatial distribution characteristics of mechanical indicators under different permeability conditions.The effects of horizontal and vertical hydraulic conductivity on the mechanical properties of pavement are initially clarified.The results show that the vertical stress of the asphalt pavement,the horizontal strain at the bottom of the asphalt layer,and the vertical displacement of the asphalt pavement in the unsaturated state increase compared to the saturated state,and the possibility of cracks but other structural diseases increases,accordingly.As the pore pressure comes lower at unsaturated state,the risk of moisture damage drops.At the same time,the effect of the hydraulic conductivity is different from that of the saturation.Compared with the horizontal direction,the vertical p hydraulic conductivity determines the seepage area of water in the pavement structure while changing the pore water pressure amplitude.Therefore,accurate measurement of the hydraulic conductivity in both directions is of great significance for obtaining an accurate road dynamic responses.The multi-directional seepage device developed in this paper can effectively improve the test accuracy of the asphalt mixture hydraulic conductivity.At the same time,the analytical solution and numerical simulation of unsaturated asphalt pavement provide basic support for the study of pavement mechanical properties...