Directional drilling, commonly called horizontal directional drilling or HDD, is a steerable trenchless method of installing underground pipelines with minimal impact on the surrounding area. Directional drilling is suitable for a variety of soil conditions.
Directional drilling is typically used to provide less traffic disruption, lower cost, deeper and/or longer installation, no access pit, shorter completion times, directional capabilities, and environmental safety.
The technique has extensive use in urban areas for developing subsurface utilities as it helps in avoiding extensive open cut trenches.
The process starts with receiving pit and entrance pits. These pits will allow the drilling fluid to be collected and reclaimed to reduce costs and prevent waste. The first stage drills a pilot hole on the designed path, and the second stage enlarges the hole by passing a larger cutting tool known as the back reamer. The reamer’s diameter depends on the size of the pipe to be pulled back through the bore hole. The driller increases the diameter according to the outer diameter or the conduit and to achieve optimal production. The third stage places the product or casing pipe in the enlarged hole by being pulled behind the reamer to allow centring of the pipe in the newly reamed path.
Pipes can be made of materials such as PVC, polyethylene, polypropylene, ductile iron, and steel if the pipes can be pulled through the drilled hole.