A New Perspective on Rutting in Flexible Pavements

This report represents a new approach to the prediction of rutting in flexible pavements. It recognizes the prominent role played by the granular layer in the stress distribution and strain accumulation in flexible pavements and diverts from the conventional continuum approach to modeling stresses in the layer. Fundamentally, the conventional requirement for the existence of the second derivatives of strains in the granular layer is replaced by a stress continuity equation that provides for stress transfer between particles through these contacts. This is developed assuming that deformation is due primarily to particle movements and is shown to be based on a nonlinear stress-strain relationship unique for granular material. In order to evaluate the rutting in a flexible pavement, the particulate theory of stress transfer is extended to predict stresses in multilayered systems consisting of granular and elastic layers. Knowledge of the nature of stress transfer and stress-strain response is next incorporated into a theory for strain accumulation with repetitive loading.