Study On The Acceptance Methodology Of Subgrade And Pavement Deflection Under Multi-index Design System

To improve the methodology and index of existing asphalt pavement designstandards, a program of the Research of Asphalt Pavement Design and Index Programwas carired out by the Ministry of Transportation; a multi-index design system isestablished. But the synthetic deflection correction coefficient in present standards iscarried out in the static index system. Mostly, the work of the check and acceptance ofsubgrade and pavement is accomplished through the measurement of deflection byBearing Plate or Benkelmen Beam. As the superiorities of testing fast andundestructively.simulating the actual vehicle load properly and so on.the Falling WeightDeflectormeter(FWD) have gradually been aware which birng it a popularity inpavement structure evaluation. For the eiffciency and the standardization of utilizingFWD in the pavement structure practice, a new method and standard for check andacceptance of subgrade and pavement deflection under multi-index design system isnecessary, in which FWD is included in the practice of deflection testing. On thispurpose, this paper carired out a lot work to investigate the methodology and standardsin subgrade and pavement check and acceptance.Based on pavement mechanical theory, ifnite element numerical method was usedto explore the principle of mechanical response of typical semi-irgid asphalt pavementstructures under both static and dynamic loads，along with the influence of contact statebetween layers. Analysis observed that the dynamic effect of load and contact statebetween layers caused the correction of theoretically calculated deflection and moduluswhich back calculated from method based on elastic layered system.On the basis of finite element method and the principle of backcalculation, theSIDIMOD was utilized to backcalculate the moduli of subgrade soil through deflectiondata collected in both indoor and in-site test section，and a comparison is carried outbetween the backcalculated results and dynamic moduli measured in laboratory, then thebackcalculatcd moduli correction coefifcient K for various soil were obtained. A methodof using backcaculated modulus for pavement structure can be applied to calculate theefifcient moduli of subgrade soil and proceed moisture correcting in the pavementdelfection check and acceptance practice.A comparison is made between deflectioncalculated from mechanic theories and values measured in field, which indicates that itis most reasonable to use central point delfection as check and acceptance indicator. Through experiment section paving, falling weight deflectormeter delfection measuirng,materials properties indoor testing, factors influence synthetic correction coefficient ofdelfection selecting and a compairson between delfection calculated by BISAR3.0anddeflection tested in-situ, both synthetic correction delfection of subgrade and pavementsurface are determined. Based on the synthetic correction coeiffcient formuladetermined, methodology for pavement check and acceptance is established. Theformula and methodology for check and acceptance were veirifed in actualproject,meanwhile, the methodology is programmed which will birng convenience inthe engineeirng practice of check and acceptance for newly constructed asphaltpavement.