First Findings from the Kansas Perpetual Pavements Experiment
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Date
2008Author
Romanoschi, Stefan
Gisi, Andrew J.
Portillo, Miguel M.
Dumitru, Cristian
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To investigate the suitability of the perpetual pavements concept for
Kansas highway pavements, the Kansas Department of Transportation
(KDOT) constructed four thick, flexible pavement structures on a new
alignment on US-75 near Sabetha, Kansas. They were designed to have
a perpetual life and have layer thicknesses close to those recommended
by KDOT’s structural design method for flexible pavements, which is
based on the 1993 AASHTO Design Guide. To verify the approach of
designing perpetual pavements on the basis of an endurance strain limit,
the four pavements were instrumented with gauges for measuring the
strains at the bottom of the asphalt base layers. Seven sessions of pavement
response measurements under known vehicle load were performed
between July 2005 and October 2007, before and after the pavement
sections were opened to traffic. The analysis of the strain data indicated
that, even during hot summer days, the strains of all four test sections
were smaller than the endurance limit of asphalt–concrete. As expected,
the strains were affected by the temperature in the asphalt layers and the
speed of the loading vehicle. The analysis of the strain signals revealed
that the transverse strain under the front axle did not recover completely
before the arrival of the rear axles, a situation causing the accumulation
of dynamic transverse strain to values higher than those of the corresponding
longitudinal strains. A comparison between the measured
response and that predicted by a linear-elastic model indicated that
the predicted transverse strains were close to half the corresponding
measured dynamic transverse strains, while the predicted longitudinal
strains were close to twice the measured dynamic longitudinal strains.
Furthermore, the predicted vertical stresses at the top of the subgrade
layer were close to five times the measured stresses.