We study experimentally and theoretically the sedimentation of gels made of strongly aggregated colloidal particles, focusing on the long-time behaviour, when mechanical equilibrium is asymptotically reached. The asymptotic gel height is found to vary linearly with the initial height, a finding in stark contrast with a recent study on similar gels. We show that the asymptotic compaction results from the balance between gravity pull, network elasticity and solid friction between the gel and the container walls. Based on these ingredients, we propose a simple model to account for the dependence of the height loss on the initial height and volume fraction. As a result of our analysis, we show that the static friction coefficient between the gel and the container walls strongly depends on the volume fraction: the higher the volume fraction, the weaker the solid friction. This non-intuitive behaviour is explained using simple scaling arguments.
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Condre et al. (2007) studied this question.