Horizontal Directional Drilling is a construction method used to install a product/use below the grounds surface on a horizontal plan without annoying the surface or above ground activities.

Horizontal drilling allows a passage, pipeline, cable etc to be installed where other techniques like open trenching would become perilous, sloppy, time intensive and on occasions impossible to build.

The Horizontal Directional Drilling procedure are composed of 3 major objectives:

1. The Pilot Bore
2. Reaming Process
3. Product Installation

The Pilot Bore

Through the use of a drillhead, which penetrates into the ground formation, a bore hole is produced under the surface in accordance with the designated bore trail. The drillhead location is monitored at all points by the use of a transmitter found in the drillhead sending information to a receiver on the surface. This information tells the operator the drillheads lateral position, depth and pitch as well as drillhead temperature The bore path may need the drillhead to led around existing services or below a structure such as a road, buildings, train line or perhaps waterway. In the whole process, drilling liquid is pumped thru the drill rods and out thru the drillhead. This specialised drilling liquid mixers with the cuttings to form a drill slurry which helps stabilise the hole, suspend cutting & stop frac-outs. Once the drillhead enters the exit pit, that has been constructed at the other end of the bore path, the pilot bore has been finished.

Reaming Process

Once the pilot hole is complete, the drillhead is removed and a back reamer attached to the drill string. The reamer is then slowly pulled back thru the hole whilst being rotated. As the reamer augments the hole, the cutting again mix with the drilling liquid being pumped thru the drill rods to help stabilize the hole and guarantee flow continues to the exit pit. Several different size reamers perhaps required to bring the hole to its elected size.

Product Installation

Once the bore hole has been enlarged to its correct size and the hole is cleaned out, the product is attached to the reamer through a pipe puller, several metres of chain and swivel. As the product is being pulled back thru the bore hole, drill slurry is forced into any voids that may a have been produced around the product. This is where the correct drilling additives used are so crucial. Once the product has entered the entry pit is it disconnected from the drill string, HDD machine is removed, site returned to its original condition and all open pits made safe including fencing.

The benefits for using Trenchless technology are many and varied but each job site should be evaluated by itself separate form as some advantages might not be as equally important as others.

• Only nominal interruption is caused to all surface movements and structures when using Trenchless technology.
• No need to excavate hard surfaces such as roads. Reducing interruption to traffic flow.
• Constructs a bore hole under the roots of trees and plants therefore causing minimum disturbance to foliage.
• Preferred methodology for installing products under rivers and waterways so reducing bridge modification and construction of overhead wires.
• Safer to the public as no long trenchers are needed.
• Multiple products can be installed in a single bore hole.
• Trenchless apparatus includes both pit and surfaced launched machines reducing set up time and expense.
• Nominal visible effect to residence while construction process is occurring.
• Time on the work site can be shortened.
• Can be guided horizontally and vertically en-ambling the bore hole to navigate through existing structures and services.

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