Permanent Deformation of a Granular Base Material

Abstract

An approach to the characterization of unbound pavement materials for mechanistic analysis of pavements is presented. To predict permanent deformation, it is necessary to evaluate the residual properties of the materials. A method for evaluation of both the resilient and residual properties from repeated load testing is recommended. The residual properties of the material are described by three functions: ( a) the slope of the permanent strain versus number of load repetitions, S, on a loglog scale, ( b) the loading stress-strain curve of the first cycle, and ( c) the resilient properties of the material. The framework for evaluation of the permanent characteristics is presented. It is based on the theory of elastoplasticity. Two models developed by Vermeer and by Desai [hierarchical single-surface (HISS) model] are described. Test results conducted with a high-quality base course are presented and analyzed. It is found that ( a) the slope S depends slightly on the confining pressure and ( b) both models describe the dependence of total strain on stress. The HISS model with eight parameters fits the results better than the Vermeer model.