These methods are limited in that they cannot take into account the stress sensitivity of the pavement materials and subgrade. The results from the study show that backcalculation methods can be used to determine the moduli of aggregate and asphalt surfaced pavement layers. Finally, a regression equation was developed for the prediction of backcalculated modulus from pavement surface deflection basin for aggregate surfaced roads. Also, for a known stress state, attempts were made to develop a regression equation which can be used to predict modulus as a function of dry density and moisture content. Attempts were made to develop regression equations relating subgrade moisture content to easy-to-measure variables, such as rainfall, site aspect, pavement thickness and elevation. Also, the backcalculated moduli were compared to laboratory determined values. The backcalculated moduli obtained from different equipment for any test site were compared to each other. The backcalculation procedures used were BISDEF, MODCOMP2, and SEARCH. The deflection data collected using NDT devices were used to backcalculate pavement layers and subgrade moduli. A total of 27 project sites were studied. Samples of the pavement materials and subgrade were taken for evaluation in the laboratory using standard methods. Soil moisture cells were implanted in the subgrade to monitor the moisture content and temperature of the subgrade. Pavement surface deflection measurements were taken using three NDT devices, namely the Dynaflect, Road Raterand Falling Weight Deflectometer (FWD). This was achieved by the use of Nondestructive Testing Methods (NDT) and backcalculation techniques. Copyright © National Academy of Sciences.This study involved the determination of the structural layer properties of aggregate and asphalt surfaced pavements for use in the evaluation of pavement load carrying capacity and the seasonal effects of moisture.
BACKCALCULATION OF PAVEMENT LAYER PROPERTIES 1989 PDF
Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. 1384, Strength and Deformation Characteristics of Pavement Structures.
In recent years pavement structural evaluation has relied increasingly on determining material properties by nondestructive deflection testing and backcalculation procedures. SYSTEM IDENTIFICATION METHOD FOR BACKCALCULATING PAVEMENT LAYER PROPERTIES
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