Analysis of multi-stage creep and swelling oedometric tests on a French marl

The paper focuses on the delayed behaviour of marls induced by a change in stress state and by the effect of water. Seven experiments were conducted in oedometric cells on marl from the Arbus tunnel (France). The samples were subjected to a single loading step (i.e one-stage creep test) or to successive loading steps (i.e. multi-stage creep test) followed, after hydration, by several unloading stages. For the creep behaviour, Lemaitre’s law is found adequate to model the viscoplastic strain, but its parameters are different for one-stage and multi-stage creep tests. As for the swelling related to the unloading stages after samples hydration, an empirical hyperbolic law provides very good results. A global model that partitions the deformation during the creep and swelling stages allows to well reproduce the measured axial deformation.