Bubbles breaking the wall: Two-dimensional stress and stability analysis

Suspensions can be deformed through rearrangement of grains during the motion of a gas-liquid interface. Regions of jammed beads at the interface, can lead to intermittent behavior in the dynamics. We study the stability of layers of saturated jammed beads around stuck air bubbles, and the deformation mechanism leading to air channel formations in these layers. We describe a two-dimensional extension of a previous model of the eective stress in the jammed packing. We discuss how the tangential stress component alters the yield stress, in particular how arching eects may impact the yield threshold. We further develop a linear stability analysis, to study undulations which develop under certain experimental conditions at the air-liquid interface. The linear analysis gives estimates for the most unstable wavelengths for the initial growth of the perturbations. The estimates correspond well with peak to peak length measurements of the experimentally observed undulations