Mechanical behaviour of granular layers and its optimisation for the pavement design of low volume roads

Mechanical properties of unbound granular materials play an important role in the design of flexible pavements for low volume roads. The aim of this paper is to present a study made to analyse the mechanical behaviour of unbound granular materials through laboratory and field load tests. This is applied to a Portuguese case study. With this purpose, two test pavements were instrumented during the construction phase with deformation gauges placed at different levels and thermoelectric couples located in bituminous layers. Strains and climatic conditions have been measured during field load tests realised in these test pavements. Granular materials were tested in laboratory using repeated load triaxial equipment. Elastic nonlinear models were verified and calibrated to describe resilient behaviour of the studied materials. These models have been incorporated in a finite element program used in modelling structural behaviour of test pavements during the load tests. Pavement response is evaluated by the strain levels at the bituminous layer and subgrade, which are the design parameters in flexible pavements. This paper presents the main conclusions based on the comparison between results from monitoring and from numerical modelling of the tests pavements behaviour in load tests