A viscoelastic-plastic behaviour analysis of expanded polystyrene under compressive loading: Experiments and modelling

Generally, when soil has poor properties (unstable or compressible soils) it is possible to use EPS foam in road construction, because this material has low density. In this case, it is necessary to investigate the mechanical properties of EPS. In this work, an experimental study and modelling investigation were performed in order to determine the EPS mechanical behaviour under compressive loading. The experimental results show that the global compression behaviour of EPS is characterised by three stages. The linear elastic stage is defined by an initial tangent modulus E* followed by a non-linear elastic part. The second stage, which is described by a plateau, is characterised by a stress threshold sigma (s)*. Finally, the densification stage corresponds to large compressive strains when the material of the cell walls is entirely compressed. Globally, the apparent density of EPS plays an important role. In fact, when the density increases 'Young's modulus and threshold stress increase, but the densification strain decreases. A phenomenological mechanical model is verified in order to simulate the EPS viscoelastic-plastic behaviour under compressive loading. This model, which is based on a super-position of viscoelastic and elastic-plastic behaviour, introduces six parameters determined by an identification technique. The results obtained in terms of the stress-strain curves are in a good agreement with the experimental data. Using "Castem 2000" finite element software, the numerical simulations were achieved in order to describe the mechanical behaviour of the EPS material. This shows that it is possible to use numerical simulation in order to compute EPS structure used in road laying.