Fracture mechanics in pavement design

Abstract

Paper presented at the 28th Annual Southern African Transport Conference 6 - 9 July 2009 "Sustainable Transport", CSIR International Convention Centre, Pretoria, South Africa.

ABSTRACT: Pavement materials are subjected to high-cycle loading regimes. Conventional design methods employ the Palmgren-Miner damage hypothesis to predict the fatigue life of pavement materials. The material itself is usually characterized in the analysis by a measured material parameter. This approach is practical and can readily be calibrated, but does have some known shortcomings. The aim of the paper is to discuss some of the limitations of empirically based, Palmgren-Miner type, damage laws. The paper also seeks to promote the use of size independent material properties to characterize pavement materials. Some material properties used in current methods, such as the concepts of strain at break and flexural strength are known to exhibit size effects. Examples of the use of fracture mechanics providing an alternative to these conventional design parameters are given in the paper. The paper shows that although much further development is required before fracture mechanics can be relied upon to fully replace the Palmgren-Miner type damage laws, some of the concepts can already be applied to improve pavement design methods.