Abstract

A. research is being undertaken herein to develop a design chart, for pavements with granular base and bituminous surfacing, as it is the most commonly used pavement structure in Australia. The design charts currently available for the design of flexible pavements, and computer programs used as tools in developing those charts, are all based on multilayer elastic theory. Furthermore, the loading is considered as static in those programs. There are few computer programs available for pavement analysis based on finite element theory and considering static loading. In this research, the finite element theory is used in place of multilayer elastic theory, and cyclic loading is considered in place of static loading. A flexible pavement structure with a thin bituminous surfacing and a granular base is modelled as a finite element model, using a general purpose finite element computer code. The surfacing and base materials are modelled as linear elastic. The subgrade material is modelled as nonlinear. The maximum displacements at a point on the surface are calculated for various number of load applications. A curve is developed for Surface deflection versus Number of load applications. Similar curves are developed, varying the thickness of the base layer. Those curves are extended, and the number of load applications required to produce a 25mm rut depth on the surface are calculated. The thickness of the base layer versus the Number of load applications required to produce a 25mm rut depth, is plotted and presented as the design chart for the design of flexible pavements. The nonlinear model used for the subgrade, is checked with a pavement structure where ALF (Accelerated Loading Facility) trials have been carried out. The calculated deflections after various number of load applications are matched with the rut depths measured after application of corresponding number of cycles of ALF load. The developed charts give more accurate representation of the behaviour of flexible pavements under traffic loading.