Research On The Structure Effect For Design Parameter Of Semi-rigid-base Asphalt Pavements

In China, the majority of asphalt pavements have been constructed with semi-rigid base.The main design input parameters of this type of pavements include thickness and modulus ofthe pavement layers and the subgrade, while the pavement design is evaluated or validatedthrough two types of design control indices namely resilient deflection at the pavementsurface and tension stresses at the bottom of each pavement layers. Obviously, there arecertain links among the design input parameters and the design control indices. The mainobjective of this research is to quantitatively study the links among design parameters andcontrol indices and optimize the pavement design through the following three main tasks:1) Based on the gray relative analysis method, the first task of this research is toinvestage impacts of pavement layer thickness and stiffness values on the resilient deflectionat the pavement surface.Through this task, all the impact factors (including layer thicknessand stiffness) were ranked in term of their importance to the resilient deflection.2) Based on the orthogonal analysis approach, the second task of this research is studyinfluence of the sub-grade modulus on the resilient deflection. Through this task, the influenceparameters were obtained for interpreting relation between the subgrade and the resilientmodulus;3) Based on the gray relative analysis method and the orthogonal analysis approach, thethird task of this research is to build links of the input structural parameters to the tensionstress at the bottom of each pavement structural layers. Through this task, all the impactfactors (including layer thickness and stiffness) were ranked in term of their importance to thetension stress.In this research, a newly developed parameter, the overall pavement stiffness, was usedto characterize the asphalt pavement structural effects on the design control indices, whichactually integrates pavement layer thickness, modulus, and other structural parameters. Basedon different calculation standards or methods, the overall pavement stiffness can be thestructural combination characteristic parameters based on surface deflection KLs, the structuralcombination characteristic parameters based on tension stress on the bottom of surface Kσs,the structural combination characteristic parameters based on tension stress on the bottom ofbase Kσb,and the structural combination characteristic parameters based on tension stress onthe bottom of sub-base Kσsb. Through the Excel curve fitting and run the HPDS software, thedifferent structural combination of pavement performance under the control index values(including surface deflection value, tension stress on the bottom of surface value,tension stress on the bottom of base value, tension stress on the bottom of sub-base value) wascalculated and a quantitative relationship between the structural characteristic parameters andpavement performance control index values were obtained. The relationship can be used as aperformance prediction model for many aspects of engineering design, performanceprediction, on the one hand, to provide a basis to reveal the relationship between the structureand properties deeply, on the other hand to reduce or avoid the arbitrariness and blindness inthe engineering design or performance evaluation, provides reference or basis for theoptimization of the design and construction program.