Search youtube for "crawl space underpinning" for some videos of a residential process.

I'm sure they're doing something more elaborate there, but in residential you do this underpinning technique if you want to replace or extend your foundation (in my case, putting a basement where there is a crawl space), where you mark the foundation into 2' segments and label them A, B, C. Then you go through and dig/cut out all the "A"s, and pour footings and foundations in place, then repeat for the Bs and Cs. I'm thinking about doing this for my crawl space just to have some more space for storage.