Effects of a nonuniform subgrade support on the responses of concrete pavement.
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2013-09-01
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ISSN:0197-9191
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NTL Classification:NTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and Performance
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Abstract:Intelligent compaction is gaining attention for its ability to spatially map the compaction effort of a pavement support layer, and it has also
been shown to be able to detect areas of nonuniform compaction, which raises the issue of what the effects of a nonuniform support
condition are on the stresses and deflections in a rigid pavement. This study considered multiple nonuniform support conditions, including
theoretically generated and predetermined and randomly assigned from measured field data. The slabs and nonuniform support
conditions were modeled using two-dimensional and three-dimensional finite element methods with input variables being axle type,
curling, and lateral and longitudinal axle movements. Overall the study found that certain nonuniform support conditions and axle
positions can significantly increase the peak tensile stress in the slab over even uniform soft support. In particular, a single slab with soft
longitudinal edge support and a slab with “randomly” assigned nonuniformities were critical cases that increased the peak slab tensile
stresses. When the slab was modeled with preexisting through-length surface cracks, it was found that the nonuniform soft edges support
conditions would result in unstable crack growth based on the significant increase in the stress intensity factor. When modeling a set of
concrete slabs over a nonuniform support based on field data, the peak tensile stresses were increased relative to a uniform support
based on the location of the wheel load relative to the nonuniformity and also based on the adjacent differences in nonuniform soil
stiffness. The field data was also statistically reassigned by normal and beta distributions to predefined area sizes, which demonstrated
that with a normal distribution, the probability of low k-values along the pavement edge increased thereby raising the probability of higher
peak tensile stresses. Overall, certain nonuniform support of concrete slabs can produce much higher tensile stresses than a uniform
support condition, particularly when considering different loading positions and curling conditions, soft support along the pavement edge,
and preexisting cracks.
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