Trenchless Construction Options - Horizontal Directional Drilling

Horizontal directional drilling (HDD) is the most commonly used trenchless process for installing water pipe.

Traditionally these applications were reserved for only roadway and river crossings. Today, HDD is
employed for a myriad of other applications where the benefits of trenchless installation can be derived.

In recent years, developments in the precision of HDD machinery, specifically the ability to monitor and steer the
pilot bore with high levels of accuracy that maintain line and grade, has also enabled the installation of gravity
sewer pipes.

HDD is performed with a drilling rig and involves three essential steps. First a pilot bore is created, covering the
distance over which the pipe is to be installed. Highly sophisticated electronics enable the drilling rods to be
carefully guided and its direction of travel to be monitored. Reamers are then pulled back to obtain a diameter
large enough to accommodate the diameter of the pipe. Simultaneously, drilling mud is pumped into the bore
to stabilise the boring and to prevent soil collapse. In the final step, the new pipe to be installed is pulled back
through the bore.

The greater hydraulic capacity of PVC pipes potentially allows a smaller hole to be drilled, allowing savings
in drilling time and cost. PVC’s higher strength compared to Polyethylene allows longer shot lengths for HDD
installations, with single lengths of over 2km having been achieved.

Restraint joint and Fusible PVC pipelines are both ideal for HDD projects