Study On Mechanical Behaviors Of Asphalt Pavement Under Complicated Tire Force

With the continuous economic development and increasing exchanges of passengers and freights among different regions,highway transportation is developing toward speediness and heavy industrialization,which results in intensely high speed and heavy loading of vehicles.In this context,studies on the mechanical behavior of asphalt pavement under heavy traffic load are urgently needed in the fields of road engineering and highway construction management.In most of the relevant research,tire force is simplified into static uniform vertical load,which could not adapt to the specific requirements of asphalt pavement design and early pavement failure mechanism research under heavy dynamic traffic loads.Research on the mechanical behaviors of pavement under complex tire forces by introducing horizontal tire contact stress into the pavement model has important theoretical significance and engineering application values to enrich and develop pavement design theory.In the current study,simulation models of vehicle,tire,and pavement were developed using multi-body dynamics method or finite element method to examine the mechanical behaviors of asphalt pavement under complex tire forces.Under typical working conditions of vehicles and pavements in China's highway transportation,the tire stress and mechanical behavior of pavements were studied from the perspective of the vehicle-road interaction system.The influences of vehicle parameters on the spatial distribution of tire force,the dynamic response of pavement,and typical failures of pavement were analyzed comprehensively.Based on the analysis,some main conclusions can be drawn.(1)Tire force can be expressed by components at three directions:vertical contact stress(CPRESS),longitudinal contact stress(CSHEAR1),and horizontal contact stress(CSHEAR2).Under steady-state conditions,these three contact stresses exist simultaneously.When tires roll freely,CSHEAR1 and CSHEAR2 are at the same magnitude with CPRESS.Most rolling states of tires during running are close to free rolling.Thus,CSHEAR1 and CSHEAR2 should be considered in the analysis of the mechanical responses of tires and pavements.Under complete braking and complete traction states,CSHEAR1 is the main component of horizontal tire contact stress,whereas CSHEAR2 can be neglected.(2)CSHEAR1 and CSHEAR2 have significant impacts on the mechanical behaviors of pavements.In particular,these components increase the equivalent stress amplitude of the pavement surface and the equivalent stress intensity factor of early TDC.However,the tensile stress extremum of semi-rigid material is controlled by CPRESS but is not influenced by the horizontal tire contact stress.(3)The spatial distribution of the tire force varies under different working conditions of vehicles.Controlling the load and increasing the tire pressure can effectively improve its ground pressure distribution.Road conditions significantly influence the tire force.CSHEAR1 is sensitive to the friction coefficient and the longitudinal slope of pavements,whereas CSHEAR2 is sensitive to the horizontal slope of pavements.(4)Common parameters of highway transportation,speed,loading rate,and tire pressure of trucks as well as the longitudinal slope of pavements can have significantly negative impacts on the service performance of pavements.Low speed,high tire pressure,and overloading are direct causes of rutting.Overloading will accelerate the expansion of early TDC.However,high tire pressure will not significantly influence the expansion of early TDC.(5)The effects of the front axle of vehicles on rutting and early TDC are indispensable.Multi-shaft vehicles more easily cause rutting as compared with single-shaft vehicles.