It's not that simple. Even pile foundations don't always go to bedrock. In fact, most of the load bearing strength of a driven pile is in the friction along t

It's not that simple. Even pile foundations don't always go to bedrock. In fact, most of the load bearing strength of a driven pile is in the friction along the length of the shaft, and the end-bearing capacity is a fraction of that. (It's intuitive if you recognize the surface area of the end of the pile is much smaller than the surface area of the sides of the pile) Soil calculations treat the soil almost as if it is a highly viscous fluid. In regards to settling - all structures settle. It is the structural engineer's job to design a structure that anticipates settling and mitigates strain in the rest of the structure. Clay is interesting, because it has a property called consolidation. If the clay is overconsolidated, that means the overburden pressure in the past is higher than the pressure on the soil now. If a clay is overconsolidated, it settles a lot less.