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Cane Cekerevac[24], Susanne Baltzer, Robert Charlier, Cyrille Chazallon, Sigur0ur Erlingsson, Beata Gajewska, Pierre Hornych, Cezary Kraszewski and Primoz Pavsic Abstract This chapter presents laboratory and in-situ experimental techniques used to describe the mechanical behaviour of pavement material at different saturation stages. The use of repeated triaxial load testing to obtain stiffness characteristics as well as […]

Routine pavement design is based on an elastic calculation, with a resilient modulus. The design criterion is, typically, a limit placed on the maximum vertical strain. More elaborated models take into account the irreversible behaviour, e. g.: • The Chazallon-Hornych model is based on the Hujeux multi-mechanism yield surface improved by a kinematical hardening; and […]

The constitutive models introduced in the previous sections express the constitutive stress-strain relation of the material. As soon as the water is involved, the material has to be considered as a multi-phase porous media with two phases: the solid matrix (for which we introduced the stress-strain constitutive relations) and the water phase. The two phases […]

New concepts have been developed to determine the long term mechanical be­haviour of unbound materials under repeated loadings. All these concepts are pre­sented in a special issue (Yu, 2005) of the International Journal of Road Materials and Pavements Design. The shakedown concept applied to pavements was introduced first by Sharp and Booker (1984). The various […]

Visco-plastic equivalent models based on an equivalent time: number-of-cycles re­lationship, have been developed by Suiker and de Borst (2003) for the finite element modelling of a railway track structure and by Mayoraz (2002) for a laboratory study of sand. Suiker has developed a cyclic densification model. It is based on repeated load triaxial tests carried […]

The plasticity theory based models require the definition of yield surface, plastic potential, isotropic hardening laws, and simplified accumulation rules (Bonaquist & Witczak, 1997 and Desai, 2002), or kinematic hardening laws (Chazallon et al., 2006). Some of these models have been used for finite element modelling of pave­ment. Now, the main concepts of these models […]

A few material models have been proposed for the development of plastic strains in unbound granular materials in a pavement structure. Lashine et al. (1971), and Barksdale (1972) tested unbound granular material in a repeated load triaxial test for 100 000 cycles. They found that the permanent axial deformation, єpb at different Fig. 9.4 Example […]

Routine pavement methods are mechanistic-empirical design methods, based on linear elastic calculations. Usually, the only rutting criterion to be used concerns the subgrade soil, and consists in limiting the vertical elastic strains at the top of the subgrade. Rarely is a criterion applied for the unbound granular layers although Dawson and Kolisoja (2004) have shown […]

The above methods define stiffness as a function of stress alone. Full incorporation of the effects of moisture (as a pressure or suction) should necessitate use of an effective stress framework (see Section 9.5). However a more simple approach, at least in principle, is to adjust the stiffness value calculated by one of the above […]

The behaviour of unbound granular materials in a pavement structure is stress — dependent. For that reason the linear elastic model is not very suitable. A non-linear elastic model, with an elastic modulus varying with the stress and strain level is, therefore, needed. For isotropic materials, moduli depend only on two stress invariants1: the mean […]