Backcalculation of Thin Air ― A Way to Cope with Slipping and Sliding Layer Interfaces

摘要

Some road test sections with suspiciously low unbound base moduli were backcalculated with a new approach. By inserting a very soft, thin layer between the bound and unbound layers small spatial movements in the interface could be accounted for. Rather than backcalculating the thin layer modulus it was assumed to be the same as the barometric pressure. Thus, the gap width was backcalculated instead. It was found that it was possible to determine the width using traditional optimization techniques. Alternatively varying the friction between layers also had the same effect. If such parameters are to be incorporated in a backcalculation software, it is important to be aware of the limits for solving layer properties. It is recommended to add routines for the uncertainty of the derived moduli.