Horizontal Directional Drilling ( HDD )
Horizontal Directional Drilling (HDD) is a method of installing underground pipes, cables, and service lines without digging trenches. This method is useful for avoiding damage to the ground surface and existing infrastructure, such as roads, railways, and rivers.
The HDD process consists of three main stages2:
Pilot Bore: An initial horizontal hole is drilled along the intended route of the final pipe. The drill bit is attached to the rotating drill pipe and pushed to the specified location. Drilling fluid is used to guide the drill bit, stabilize the drill hole, and carry soil and rock cuttings out of the drill hole.
Reaming: A reaming tool is attached to the drill pipe and pulled back through the drill hole to enlarge the hole. This process is repeated several times with larger reaming tools until the hole reaches the desired size.
Product Pipe Installation: Once the hole is large enough, the product pipe is pulled through the enlarged drill hole.
The HDD method has several advantages, such as reducing environmental impact, minimizing traffic disruption, and allowing pipe to be installed under infrastructure that is difficult to reach with conventional methods.
