Implementation framework of the UIUC aggregate base rutting model

This paper presents findings from a research study focused on calibrating and improving the robustness of a permanent deformation model for unbound aggregate base/subbase materials, recently developed at the University of Illinois and referred to as the UIUC rutting model. The model provides estimates for permanent strains as a function of load cycles, applied deviator stress, and the ratio of mobilized shear stress to strength. Sixteen aggregate materials were tested for permanent deformation both at their source gradations, and an engineered gradation. Based on multiple linear regression analyses, the UIUC rutting model parameters were determined to estimate the laboratory-measured permanent strains with high accuracy. Constrained and stepwise regression statistical approaches were employed to reduce variability in the regression model parameters and express the model parameters as function of material properties such as shear strength, morphological shape properties, gradation, and compaction characteristics. Results from stepwise analyses indicated that the most accurate predictions could be achieved by considering particle shape properties. Finally, a framework was established to predict unbound aggregate permanent deformation trends of flexible pavement base/subbase layers using the UIUC model parameter equations obtained from stepwise regression, along with the physical/mechanical properties of the aggregate materials determined from standard laboratory tests.