I sometimes encounter a shallow foundation that has a finite layer of suitable soil below it and then underlain by soft Clay. I am trying to use the Boussinesq equations to generate footing stress contours in color beneath the footing. This way, I can see the stress at the top of the soft clay below the center of the footing and at the edge of the footing. So it will need to to generate "onion like bulbs". Any ideas how this can be done in any low cost calculation tool? Thanks.