Research On The Pavement Behaviorand Its Mixture Design For Long And Steep Slope Asphalt Pavement

It is inevitable to emerge the long and steep slope when designing highway route formountain regions. The long and steep slope not only has obvious impact on vehiclesecurity and traffic capacity， but also leads to serious pavement distress such as ruttingand traction. All above have been bottleneck of developing free way in mountain regions.So it is necessary and extremely important to analyze damage behavior of asphaltpavement on the long and steep slope and study design method of asphalt mixtureapplicable for the long and steep slope.On the road section with long and steep slope， the vehicle speed is always low andvaried largely， also the acceleration and breaking is frequent. The influence of the vehiclespeed and longitudinal grade on shear stress of asphalt pavement was analyzed accordingto Finite Element principle. The reasons that pavement rutting yields on ascending graderoad and shear distress on falling grade road were analyzed. The shear strength index ofasphalt mixtures utilized in long and steep slope was recommended according to theallowable shear stress and structural strength coefficient of pavement. The viscoelasticityof asphalt mixture was analyzed， and the results showed that the main factors forpavement deformation on long and steep slope are temperature， vehicle speed andloading.The asphalt pavement temperature in high-temperature period of summer andlow-temperature period of winter were measured by the manual and automaticallymeasuring methods. And the variation discipline of temperature in pavement surface andinterior were analyzed with the temperature changing. The results showed that: the weatherconditions have great influence on air and pavement temperature. The temperature ofpavement surface and air temperature is varied synchronously and the delaying timeincrease as the pavement depth increasing. Temperature fluctuation is small in the winter.The air temperature and surface temperature， temperature gradient has good correlativity.A direct shear device was developed so as to study the anti-shear performance ofasphalt mixture utilized in the long and steep slope. Moreover， the standard shear testmethod and parameters and evaluation indicators were recommended. The influences of mix type， asphalt type and amount， air void of mixture and other factors on the shearstrength of asphalt mixture were analyzed. The research results showed that shear strengthof SMA was greater than AC. The shear strength of asphalt mixtures always increase as theviscosity of asphalt and the nominal maximum particle size increase. The shear strengthwas related with the dynamic stability of asphalt mixture， but they can’t substitute foreach other.The relationship of temperature， loading rate， load between Dynastic Stability andrutting depth are analyzed. The results showed that they are well fitting to exponentialfunction. Moreover，equations utilized for calculating the dynastic stability varying withsingle factor and multiple factors were established. The required dynastic stability could becalculated out by the above established equations.Finally，a design method of asphalt mixture suitable to road section with long andsteep slope was proposed on the basis of analyzing the research advance of design ofasphalt mixture. The key points were to verify the anti-shear performance and dynasticstability.