A PAVEMENT ANALYSIS AND STRUCTURAL DESIGN PROCEDURE BASED ON DEFLECTION

Recognition of flexure cracking as a primary mode of distress of asphalt pavements in New South Wales, Australia, highlighted the need for a structural design procedure based on deflection. As the Benkelman beam was considered the most suitable equipment for measuring deflection for general design purposes, it was felt necessary in the first instance, to develop a pavement analysis technique to interpret the Benkelman beam measurement of deflection. The pavement analysis technique involved analysing the Benkelman beam deflection bowl using elastic theory to assess the flexibility of the subgrade and the overall flexural strength of the pavement. The elastic theory analysis was tested both theoretically and empirically to define the limits of its application and to provide the confidence required to use it in practice. In-situ non-destructive testing has particular application to reconstruction and overlay design and therefore the analysis was developed into a design procedure for this purpose. As the overall flexural strength of the pavement was expressed in terms of an equivalent thickness of a standard base material, the design procedure used the basic AASHTO pavement model. It involved designing the pavement to a design Benkelman beam deflection this was determined from the performance of the existing pavement in relation to the TRRL design deflection levels. This paper presents the pavement analysis technique and the structural procedure for reconstruction and overlay design. It also includes an example of an overlay design to demonstrate this procedure. /Author/