Numerical simulation of granular materials behaviour for unbound base layers used in Algerian pavement structures

Structural analysis of flexible pavements has been and still is currently performed using a multi-layer elastic theory. However, for thinly surfaced pavements subjected to light to medium volumes of traffic, the importance of non-linear stress-strain behaviour of unbound granular materials (UGM's) requires the use of more sophisticated numerical models for structural design and analysis of such pavements. In this work, an axisymmetric finite element model coupled with a shear volumetric strain model is utilized to simulate the nonlinear resilient behaviour of two local unbound granular materials used in Algerian pavements. This model is included herein to adequately incorporate the material non-linearity due to the stress and stiffness dependency of the granular layers in flexible pavement analysis. The numerical performance of the finite element model is examined with regards to its capability of representing adequately the granular material non-linearity under various stress conditions including low values of mean normal stress and large values of shear stress ratio. In addition, the sensitivity of pavement design criteria to the likely variations of asphalt layer thickness and mineralogical nature of unbound granular materials typically used in Algerian pavements structures are assessed and conclusions of engineering significance are formulated.