Building numerical and experimental factorial analysis of pavements' edge failure
Pavement edge failure has been encountered on many New Zealand state highways due to the lack of lateral support and the encroachment of heavy axle loads onto the edge of pavement. The main objective of this research work is to investigate the different factors affecting this type of distress. A three-dimensional finite elements model was designed to simulate different loading and shoulder conditions. A half fractional factorial experimental design was made to study five factors, namely, shoulder width, shoulder stiffness, axle load, tire pressure and pavement thickness. Each factor was studied at two levels to simulate extremely low and high conditions. Before carrying out the experimental analysis, a careful examination of the finite elements model was made to ensure accurate predictions. The multilayer elastic solution was carried out using Circly and Everstress software. The results of the multilayer and finite elements analyses were compared to actual measurements of vertical strains using the Transit New Zealand accelerated test track facility (CAPTIF). None of the models provided a perfect match between the measured and predicted vertical strains. The multilayer linear elastic solution and the three dimensional finite elements solutions were reasonably close. The order of importance of the different factors relies on the type of response and the location of that response. The shoulder stiffness was the most important factor affecting the maximum deflection under the outer wheel followed by the axle load, pavement thickness then shoulder width. For the compressive strain at the top of the subgrade and the maximum deflection between dual, the order of importance of factors was different. The shoulder stiffness, width and thickness played a significant role in distributing the stresses and strains on the top of the subgrade thus controlling the edge failure.