excavate under existing foundation slab. Insert pile into ground. Jack up to slab level to take load. I believe this is the rough process. They are used in underpinning work I believe. Any good foundation textbook will give you a better explanation.
Hubbell Power Systems distributes both Chance and Atlas resistence piers, aka jacked piers. There are several on the market but these guys have been around for a long time. Hayward Baker Inc is an installer of these products in North America.
