This paper describes the development of an asphalt rehabilitation design procedure that is aligned to the Transit New Zealand approach to the design of granular overlays. The proposed procedure uses the strain response of the existing pavement and its past performance, in terms of past traffic load, to determine a unique subgrade strain criterion for the pavement (sub)-section under consideration. After postulating a trial overlay thickness, the overlaid configuration is mechanistically analysed and checked for compliance against subgrade strain and asphalt strain requirements. The procedure takes the `remaining life' of an existing asphalt surface layer into consideration if the latter is deemed to be in sound condition at the time of rehabilitation. Simplified procedures to adjust the moduli of stress dependent materials in the overlaid configuration are presented. Simple relationships are presented which express these adjustments in terms of the characteristics of the adopted pavement model. These relationships were generated from mechanistic analyses of many pavement configurations using a range of realistic material characteristics. At this stage these relationships have only been developed for conventional pavement configurations comprising sealed unbound granular base layer(s) over cohesive subgrades. (A)
Abstract