When you're putting up a new building, you have to check the soil underneath for stability. How deep do you typically have to check? What's the extent of your "due diligence" when ensuring that a building won't collapse because of unstable ground? I imagine there might be different rules in different jurisdictions, but is there a typical, ballpark depth?
(Relatedly: Has a building ever collapsed because of unstable conditions below the checked area?)
I'm a total newbie, and I apologize for the many flaws you will be able to spot in this question.