Upgrading Pavement Design

1275 Words Jan 30th, 2018 5 Pages
1.1 Background
Before the 1920’s, pavement design consisted mainly of major thicknesses of layered materials to provide strength and protection to weak subgrade. The pavement design was predominantly against subgrade shear failure. During those times, experience based on success and failures of previous projects was used to formulate pavement design methods. As time wore on and experience grew, several design methods based on shear strength were developed.
Meanwhile, the increased traffic volume led to changes in the design criteria. In consideration of subgrade support provision, pavement performance through ride quality (smoothness) and surface distresses that increase the deterioration rate of pavement structures had to be evaluated. The attention was then mainly drawn to pavement performance rather than shear strength.Methods based on serviceability were developed based on test track experiments. The AASHTO design guide was then developed after the AASHO Road Test in the late 1950’s. Although test track experiments showed good accuracy, they were valid only for materials and climatic conditions for which they were developed. This called for new materials which also had their own failure modes (e.g permanent deformation and fatigue cracking) to be used in pavement structures, hence the development of new design criteria to incorporate such failure mechanisms.
Empirical design, Mechanistic design and Mechanistic-Empirical design are the three main…