OUTLINE OF AN ANALYTICAL APPROACH TO OVERLAY DESIGN . THIRD INTERNATIONAL CONFERENCE ON BEARING CAPACITY OF ROADS AND AIRFIELDS. PROCEEDINGS, NORWEGIAN INSTITUTE OF TECHNOLOGY, TRONDHEIM, NORWAY, JULY 3-5 1990. VOLUMES 1-2

This paper points out some limitations of the use of empirically-derived deflection-based models in the design of overlays for relatively weak pavements whose construction history is poorly documented. Empirical performance models of this type have been developed systematically for pavements that: (1) have been designed with respect to support conditions, anticipated loading and likely failure mode; (2) are composed of layers of specified material, each of which has a recognised structural role. These models cannot be applied with confidence to the majority of the world's primary roads, whose structural performance has not been analysed long enough for these assumptions to hold. The authors consider that structural analysis is a more comprehensive and satisfactory approach for such roads; they outline a procedure where deflection data is used, together with established theory, to determine the fundamental characteristics of existing pavements. Knowledge of these characteristics permits overlay design to be performed by a process of structural analysis incorporating appropriate performance models. Extensive data about deflection and support conditions will be used to refine the preferred approach with the aim of developing a complete design methodology. (TRRL)