What Does Helical Cut Mean?
A helical cut, in the context of trenchless pipeline removal (TPR), is a helical or spiral-shaped cut made on a target pipe in order to remove it from the ground. The helical cut on imparts a spring action to the pipe, reducing its effective diameter and enabling easy removal from the ground. The helical cut on the pipe is made using a water-jet cutting machine that is inserted into the host pipe.
Trenchlesspedia Explains Helical Cut
Until recently, the only way to remove buried pipelines was to excavate them. Otherwise, they could simply be abandoned. A pipeline can be decommissioned by cleaning, evacuation and cement mortar filling. However, the utility owner is still considered responsible for the pipeline, as it still occupies land. When such a pipeline is removed from the ground, the pipeline owner is free from all related obligations.
TPR, like other trenchless installation techniques such as pipe jacking and horizontal directional drilling (HDD), requires entry and exit pits for the launch and retrieval of equipment and pipe. TPR is conducted by performing a helical cut on the inside of the pipe using water-jet cutting. This causes the pipe to behave like a spring, effectively reducing its cross-section and therefore its soil-to-pipe friction. This allows the pipeline to be pulled out easily.