Salinity effects on the erosion behaviour of MX-80 bentonite: A modelling approach

The erosion behaviour of bentonites is influenced by the ions concentration to which they are exposed, which could lead to link the erodibility of bentonite to salinity. However, changes in salinity produce further changes in bentonite hydration and swelling that are not always considered. The aim of this work is to apply a numerical model to inspect the influence of salinity in the erosion behaviour of MX-80 bentonite, analysing the effect of swelling on erosion. To this end, a coupled hydro-chemo-mechanical and erosion model, which considers the expansive behaviour of bentonite as a function of salinity, and a hydro-mechanical model with a salinity-dependent erodibility coefficient are used to simulate pinhole erosion laboratory tests with saline waters. The results of the simulations illustrate that the influence of ion species concentration in the erosion behaviour of bentonites does not need a change in erodibility to be reproduced. On the contrary, they show that hydro-chemomechanical effects, and especially the changes that salinity induces in the swelling behaviour of bentonite, play a key role in erosion. Taking them into account leads to a more consistent formulation approach that can explain the observed behaviour, and, for that reason, such an approach is strongly recommended to analyse bentonite erosion processes.