Improving the Foundation Layers for Pavements: Effects of a Non-Uniform Subgrade Support on the Responses of Concrete Pavement - TPF-5(183)

(2014) Improving the Foundation Layers for Pavements: Effects of a Non-Uniform Subgrade Support on the Responses of Concrete Pavement - TPF-5(183).

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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 non-uniform compaction, which raises the issue of what the effects of a non-uniform support condition are on the stresses and deflections in a rigid pavement. This study considered multiple non-uniform 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 non-uniform 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 non-uniformities 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 non-uniform 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 non-uniformity and also based on the adjacent differences in non-uniform 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 non-uniform 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.