Horizontal Directional Drilling
HDD uses a steerable drilling system to allow a pilot hole to be drilled along the required alignment, then resizes via a series of backreamers for the installation of pipes, conduits and cables or other services. Typically this type of drilling is done in a shallow arc using a surface-launched drilling rig but can also be pit launched. The construction of these pits for a HDD operation can be relatively small compared with those required by other Trenchless methods.
The process is generally conducted in four main stages:
- Design of the bore path
- Drilling of a pilot bore which involves the location and steering of a drill bit along the pre-determined bore path from the entry pit to the exit pit
- Staged reaming to open the borehole to the required size
- Installing the product pipe by pulling through the pre reamed borehole