Evaluating permissible subgrade rut depth in pavement design

In the design of a pavement, the permissible rut depth and permissible resilient vertical strain at the top of the subgrade at the end of the construction stage (i.e. before the placing of the bituminous layer) are used to select the appropriate thickness of granular material. However, usually the only available data for the subgrade is the resilient modulus, which is estimated from the California Bearing Ratio. This paper examines the application of a new three-surface kinematic hardening model for the subgrade in a finite-element analysis to evaluate the rut depth and resilient vertical strain at the top of the subgrade at the end of the construction stage. The resilient modulus for the subgrade is determined by examining the stress changes at different depths in the subgrade, for different thicknesses of granular material, and applying such stress changes to simulated triaxial samples for 50 cycles to compute the resilient modulus at different depths for input to a layered elastic analysis, in order to...