Flow through a porous media, e.g. the ground, exerts a body force on the media. If the porous media is bounded by an impervious portion of a model, that seepage through the porous media exerts a pressure on the impervious part. More generally, one could model the impervious portion as simply a very impervious porous media. The body forces can then be applied to the whole model to obtain stresses, strains and displacements. More interestingly, if the impervious portion separates partly from the porous portion, we would expect to need an interactive solution because the permeability must increase where there’s separation or a a change of the stress in the media.
Comments on how Calculix could be used for this non-linear coupled seepage-mechanical problem would be appreciated.