Lyesse Laloui[22], Robert Charlier, Cyrille Chazallon, SigurOur Erlingsson, Pierre Hornych, Primoz Pavsic and Mate Srsen
Abstract This chapter deals with the effects of water on the mechanical behaviour of pavements. The analysis is based on constitutive considerations. Constitutive models devoted to both routine and advanced pavement analysis and design are introduced and both the resilient behaviour as well as the long term elasto-plastic approaches are presented. As soon as the approach considers the material as a two phase (solid matrix and a fluid), the introduction of the effective stress concept is required. In the last section an analysis is made on the extension of the constitutive models to the characterisation of partially saturated materials.
Keywords Constitutive models ■ resilient behaviour ■ elasto-plastic models ■ effective stress ■ suction effects
Road structures and the underlying soil are subjected to traffic loading. Their mechanical behaviour depends on their initial state, the hydraulic conditions and the temperature. The numerical prediction of the behaviour of such material under such conditions is not a simple matter and the user needs, therefore, to make use of comprehensive constitutive models that include a coupling of the mechanical, hydraulic and thermal aspects. The aim of the present chapter is to present an overview for such constitutive modelling, in particular covering the modelling of effects of water on the mechanical behaviour of pavements.
After first summarising the underlying reasons for the type of mechanical behaviour observed, this chapter presents a consideration of the constitutive relationships of the materials that comprise the pavement and embankment layers. It provides an introduction to the following constitutive models that may be employed in routine and advanced pavement analysis and design:
• Resilient models: the k-0 model and the Boyce model and their derivatives; and
• Long term elasto-plastic models. These models are split in four categories:
о Analytical models; о Plasticity theory based models; о Visco-plastic equivalent models; and о Shakedown models.
Routine pavement design is mostly based on an elastic calculation, using a resilient modulus and Poisson’s ratio for each layer. The design criterion is usually limited to the maximum vertical strain for a given loading condition. More elaborate models take into account the irreversible behaviour, e. g. the Chazallon-Hornych model, the Suiker model and the Mayoraz elasto-visco-plastic model. References to each of these models is given at the appropriate place in the text.
The final part of the chapter discusses how these models can be adapted to take into account and replicate the effects of variations in suction that occur in partially saturated soils and aggregates. Some suggested research topics are presented towards the end of this chapter.
