PREDICTION OF TOP-DOWN CRACK INITIATION AND CRACK GROWTH IN HOT MIX ASPHALT PAVEMENTS

摘要

It has long been accepted that fatigue cracking of hot-mix asphalt pavements is a major mode of premature failure. This paper presents a new viscoelastic crack growth simulator for asphalt pavements. The pavement structure is modelled with a new viscoelastic displacement discontinuity boundary element method. This new numerical method provides an attractive alternative to finite element-based methods for modelling crack initiation and crack growth. Meshes are only required on the boundaries of the pavement system, including cracks. Crack growth is addressed by adding more elements in regions of crack growth. The crack growth law employed was also developed at the University of Florida. A fundamental energy-based threshold is used to determine crack growth and the direction of crack growth, and viscoelastic mixture properties are used to determine the rate of crack growth. The model requires the determination of only four fundamental mixture parameters that can be obtained from less than one hour of testing using the SuperPave™ Indirect Tension Test (IDT). These parameters can account for micro-damage, crack propagation, and healing for stated loading conditions, temperatures, and rest periods. The new crack growth simulator is used to model typical Interstate asphalt pavements in Florida. The fracture simulator is shown to predict top-down crack growth patterns in hot mix asphalt pavements observed in the field. Tensile conditions at the top of the modelled pavement due to cyclic tire loads are shown to result in the eventual initiation and growth of vertical cracks that start at the pavement surface and propagate downward. Finally, the predicted cracking performance of several Interstate pavements in Florida is shown to rank in the same manner as observed in the field.