Pavement design means selecting materials and determining layer thicknesses so that the road fulfils the performance requirements for a chosen period. Mechanistic design methods make it possible to adapt designs to the particular conditions. The need for a flexible design system is motivated by the development of vehicles and especially tyres (increased inflation pressure and wide base tyres). In recent years, development has taken a direction that is unfavourable in regard to road wear.
An expected increase in usage of secondary and recycled road materials in the future is a further motive for a flexible design system. Work on developing a flexible design system for Swedish conditions has been commissioned by the Swedish National Road Administration and was carried out during the period 1987-1994. The result is described in this report. The aim of the project was to develop a user-friendly and flexible design system for road pavements which is suitable for Swedish conditions.
The following three principle sections are required for the calculation of the bearing capacity of road pavements based on a mechanistic approach:
- A calculation method for the determination of stresses and strains in the road structure.
- Knowledge of the mechanical properties of the road building materials and of the subgrade, primarily stiffnesses or resilient moduli.
- Design criteria or design values for the stresses and strains that are critical for the bearing capacity of the road structure.