ABSTRACT
The Canadian economy relies heavily on the extraction of natural resources. In that context, low-volume (mostly unpaved) roads play a major role in the socioeconomic development of the country. Up to now, empirical design approaches have been used for these roads but the current trend in pavement engineering is to adopt mechanistic-empirical design procedures. Therefore, a research project was undertaken to develop a mechanistic-empirical design procedure for unpaved roads. A small-scale heavy vehicle simulator was used on pavement structures built over four different sub grade soils in a laboratory size test pit. The experimental pavement structures were instrumented to measure stress and water content throughout the pavement layers, surface rutting, as well as permanent and resilient strain at the top of the sub grade soils. A multistage load sequence was applied to the pavement structures to determine the relationship between permanent deformation, the number of load cycles and the characteristic resilient strain for various stress levels. The results were used to develop a Wöhler curve relating resilient strain and the required number of loads to reach a rutting failure criterion at the top of the sub grade. Finally, the proposed empirical transfer function, validated with field measurements, has been coupled with a multilayer elastic analysis to complete the procedure for unpaved roads. The results from this study were compared with other available methods to validate its reliability.
