Here is a video that shows how to jack up a house or addition to a house to replace a rotten steel pier.
In this video I replace the steel piers that were holding up an addition to the house because several were rotten.
To do this I put jacks on either side of a temporary beam under the structural beam attached to the pier. This allowed for a large enough span to dig out the old steel pier. I placed two cinder block pads on either side of the beam. This allowed for one pad for the jack and one pad for additional cinder blocks as a safety measure if the jack failed.