- The minimum specification for guided boring shall be as follows:
- Pipes shall be fitted behind a boring head and follow the pipe, driven through the ground by the boring machine, after predrilling a pilot hole.
- Excavation of the face shall be carried out by the boring head, with the spoil removed by slurry pumping, or auger.
- The applied jacking force shall be distributed between the tunnelling head and the last pipe in the pipe string.
- The boring head uses the pilot hole for grade and directional control.
- Where PVC-U pipes with restrained rubber ring joints are used for boring, the maximum length of boring shall be 120m or as recommended by the pipe manufacturer.
- Any bending of the pipes, boring or tensile loads applied to the pipe during insertion into the bored hole shall not exceed the manufacturers recommendation.
Definitions in this section