Modelling the evolutive behaviour of compacted marls considering the presence of the fragments
DOI:
https://doi.org/10.24849/j.geot.2018.143.07Keywords:
Compacted marls, unsaturated soils, evolutive behaviour, deformationsAbstract
Some embankments of A10 Motorway were constructed with compacted marls, which consist of a set of fragments whose dimensions and structure depend on the compaction process adopted. Because marl is an evolving material, the fragments of marl suffer heavy physical degradation when subjected to atmospheric actions (essentially wetting and drying), resulting in settlements that may have consequences on the behavior of the embankments. Oedometric tests on the compacted material were performed in order to characterize its behavior when subjected to wetting-drying cycles. An evolution from rockfill-like behavior (when there is still no degradation of the fragments) to behavior typical of clayey materials (after degradation) was observed. This paper presents the study carried out to understand this phenomenon, as well to define an adequate constitutive model for the compacted material. The first part focus the study of the mechanism of degradation due to saturation, based on a finite element model of a fragment of rock, adopting a constitutive model for unsaturated soils. The second part presents the constitutive model defined for the marl fragment considering its physical degradation through a damage parameter. This model is then incorporated in the model defined for the compacted marls presented in the third part, used to simulate the tests. It is an elastoplastic model with hardening and softening, defined in total stresses and considering suction as state variable. Two structural levels are considered (fragments and their arrangement) as well as their interaction.
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