In most cases, an abandoned pipe is required by law to be removed or correctly decommissioned by being sufficiently filled with grout. This will prevent future collapse and the creation of voids. Improperly decommissioned piped can cause settlement to the topsoil or the substrate of the roadbed.
Most commonly, cement grout is used. Most pipes are open-ended or have a vent to void the air pressure as the grout is injected. The second option is to grout the pipe with Polyurethane foam. The polyurethane foam is dispensed using a long tube, and injection begins after the tube is inserted into the entire length of the pipe run. Once the product begins to flow, it flows toward the entrance port (now the grout’s exit) as a liquid and expands up to 20 times its volume as a closed-cell, structural foam. The pressure is voided through the entry point as the chemical reaction begins and the expansion occurs. Once the polyurethane foam expands and sets, the tubing is cut below grade and buried.