Seasonal and Spatial Variation of Subgrade Response
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Date
2000Author
Hossain, Mustaque
Romanoschi, Stefan
Gisi, Andrew J.
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Temperature, subgrade moisture content, and Falling Weight Defleetometer
(FWD)-deflection data were collected monthly on four asphalt pavement test sections
in Kansas for a year. The subgrade moduli were baekealeulated using the elastic layer
theory. It was found that for almost all sites, the monthly variation in subgrade
moisture content was not very significant over the seasons. The patterns of subgrade
response, in terms of subgrade moduli versus time, simulated sine-shaped forms
signifying a possible temperature effect. Higher variabilities across the site were
associated with the extreme temperature conditions, usually very low or high average
pavement temperatures. In all cases, the measured precipitation was nominal thereby
excluding this climatic variable as a major factor. Extreme test temperatures, both
high and low, result in higher variation of measured deflections and subsequently,
backcalculated subgrade moduli across a site. Thus, some variabilities in
baekealculated subgrade moduli can be minimized by conducting FWD tests in a
moderate temperature regime. The analysis of variance (ANOVA) indicated that both
seasonal and site variabilities can be significant. ARer correction for temperature,
variations in deflections and moduli become approximately equal to the site
variabilities which was also eorrfirmed by ANOVA.