There are plumbing companies that advocate tunneling under the concrete slabs of houses to replace pipes rather than jackhammering them from the top. How do these companies backfill their tunnels after the repairs are complete?
Perhaps many companies that do jackhammering don't properly backfill. To do that would involve having the proper sand or gravel bedding under the pipes and under the new concrete. However, its hard to imagine getting those details correct when backfilling a tunnel. Can a person put down a layer of sand or gravel and compact it when backfilling sideways?