Current issues for mechanistic pavement design

Abstract

Mechanistic pavement design programs such as CIRCLY are used to calculate elastic strains at subgrade level and at the underside of asphalt and stabilised layers. Pavement life is then calculated using empirical equations that relate these strains to load repetitions that cause unacceptable rutting of the surface, or cracking of the asphalt and stabilised layers. This paper discusses four issues currently faced by designers in using to produce pavement designs that are consistent and appropriate. The issues are: ● the choice of appropriate failure criteria ● the treatment of vehicle wander ● negative vertical subgrade strains that can lead to anomalous design results for some pavement geometries ● design of asphalt-surfaced granular pavements, The first three issues primarily impact the design of heavy duty pavements. The last issue relates to proposed changes to the Austroads (1992) Pavement Design Guide as published in the 2001 Draft Guide (Austroads, 2001).