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Response of Granular Layers in Flexible Pavements Subjected to Aircraft Loadings.
ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS GEOTECHNICAL LAB
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Airfield pavement design is a complex blend of relatively simple linear elastic theory, fatigue concepts, correlations with small-scale and full-scale and full-scale tests, and pragmatic adjustments to reflect observations of in-service pavements. The granular base and subbase have always posed the most difficult analytical problem in traditional pavement design methodologies. For this reason, the granular layers have never been treated explicitly in design as have the asphalt concrete AC layer and subgrade layer, which have used predictive models for cracking in the AC and rutting in the subgrade as a function of linear-elastic strain and material properties. Instead, these granular layers were carefully specified in terms of gradation, plasticity, and in-situ density to minimize deformation under traffic. However, todays designers are being asked to predict pavement performance under a variety of nonstandard conditions. This is a far more complex task than simply providing safe thickness and specifications for the material. To deal with this new challenge, the design community must have material models that predict cumulative deformations under repetitive aircraft loads. In order to apply these material models, mechanical response data are required to calibrate the necessary model parameters. The parameters used to define strength, failure, and deformation properties must he defined for any material to he modeled. This report describes the constitutive model requirements, laboratory tests, and analysis used in developing a response model for an unbound granular base course typical of an airfield pavement.
APPROVED FOR PUBLIC RELEASE