Directional Boring (HDD)

Definition - What does Directional Boring (HDD) mean?

Directional boring is a trenchless construction technique used to install underground piping, conduits, and cables along a pre-determined bore path using a surface launched drilling rig. This method is considered to be low impact and is often preferred over conventional pipe installation techniques since no excavation is required. Directional boring is best suited for applications where minimum disturbance to the surrounding areas is necessary.

Directional boring is also known as Horizontal Directional Drilling (HDD) or Directional Drilling.

Trenchlesspedia explains Directional Boring (HDD)

Directional drilling gets its name due to the fact that the drill bit is steerable from a remote location. Using a transmitter installed near the drill bit, operators can track and make adjustments to the bore path via a control console at the ground surface.

Free Download: An In-Depth Look At the Horizontal Directional Drilling Process


Directional boring is usually done in three phases. Firstly a small pilot hole is drilled which outlines the predetermined bore path. Next, the hole is enlarged to the required diameter using a larger diameter bit called a reamer. Finally, once the hole is large enough to accommodate the pipe, the pipeline is pulled through the enlarged hole for a continuous piping segment spanning the entry and exit holes.

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