How to Assess Elastic Properties of Heterogeneous Pavement Layers

Abstract

Backcalculation of elastic moduli is a common mechanistic approach for pavement overlay design. The method contains a model for assessing stresses and strains in various parts of the structure predicting the bearing capacity and future expected life. The precomputer era model was based on a single surface deflection only, which could be elaborated to various states of the loading, temperature and materials. Today, most pavement engineers analyze the shape of a deflection basin, allowing for a 3-dimensional view of the structure. Thus, we assess different elastic properties for a number of layers in the structure. By changing the nature of the load by magnitude or duration we can also derive non-linear properties often by using finite element modeling. However, if too many properties are being solved at the same time, there are two drawbacks. One is the long computational time being required, the other is that solutions may not be robust. So many pavement engineers use e.g. a standard load, a standard temperature et cetera. Unfortunately, in such cases it is difficult to use heterogeneous layers in the model, like coating and penetration binders. It has been suggested that such layers are treated as two separate ones, but one of their key functional roles of eliminating sliding interfaces is then being forfeited. The present paper suggests a guide to assess appropriate elastic moduli, as well as layer thickness and layer interface friction that could be used for linear elastic analyses.