What Does Backfill Mean?
Backfill is the material excavated from a bore which is then used to refill gaps and shore the hole. Backfill serves to fill gap between the casing and the conduit, pipe and other utilities in a two-pass lining system. Sometimes the material used for backfilling is cellular grout or pneumatically placed sand. Backfilling is done to increase performance and life of the pipe system, while also reducing maintenance costs. Pipes that are not backfilled properly often face settlement issues.
Trenchlesspedia Explains Backfill
The requirement for backfilling can arise due to many reasons such as the depth of pipe installation, the method of trenchless excavation, soil and pipe settlement concerns, groundwater level, site geology, the diameter of excavation, material of pipe used, and corrosion. The effects on the carrier pipe and other utilities must be considered in terms of what material is used for backfilling, pumping distance, mix density, the buoyancy of pipe, conduit and other utilities and heat of hydration. The grout density should be such that it takes into account the groundwater or flowing/seeping water that is present at that depth. In such cases, the wet density of the grout should be greater than that of water. The decision to backfill should be made early in the design process after considering the prevalent conditions in order to prevent loss of time and cost escalation.