Professional Answer

HDD stands for Horizontal Directional Drilling, a trenchless technology used to install underground pipelines, conduits, and cables with minimal disruption to the surface. It is a highly effective method for laying power cables, telecommunication lines, and other utilities underneath obstacles like roads, rivers, railroads, and buildings without the need for extensive excavation.

The process involves three main stages:

1. Pilot Hole Drilling: A steerable drill bit is launched from a surface rig and guided along a predetermined path to create a small pilot hole.

2. Reaming: Once the pilot hole reaches the exit point, a reamer is attached to the drill string and pulled back through the hole, enlarging it to the required diameter.

3. Pipe Pullback: The power cable or conduit is attached to the reamer with a Swivel and pulled back through the enlarged bore, effectively installing the utility without disturbing the ground above.