An Improved Permanent Deformation Model for Unbound Aggregate Base Course
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Permanent deformation of unbound base course materials under flexible pavements continue to be a significant source of the rutting observed at the surface. The permanent deformation behavior of unbound aggregate bases (UAB) has been documented by several authors. Several models have been proposed to predict the permanent deformation (rutting) occurring in the UAB. Most of the models do not take into account the stress dependent characteristics of UAB or have parameters which vary with stress state. An improved model has been developed at Texas A&M University which includes the stress dependency in the model and this new approach has been validated. This new model incorporates power functions of the first and second invariants of the stress tensor directly in the model along with the ε0 , ρ , and β from existing single stage models. Several previous models attempted to achieve this by using the stress as a parameter in the fitting coefficients. This left many with relatively low values of R2 or with widely varying coefficients for a range of stress states. By using the stress state directly in the model, a generalized set of fitting parameters for a given material type have been generated. Using these generalized fitting parameters, it is shown that the new model fits the experimental data on a fundamental level.
Droddy, Charles Vance (2015). An Improved Permanent Deformation Model for Unbound Aggregate Base Course. Master's thesis, Texas A & M University. Available electronically from