What is Horizontal Directional Drilling?

Horizontal Directional Drilling commonly referred to as HDD is a trenchless method of installing new underground services. The product pipeline to be installed is recommended to be High-Density Poly-Ethylene (HDPE) this is due to its flexibility, strength, and life span. However, we can install steel pipelines/sleeves provided there is sufficient space to dig a pit to allow us to launch the steel pipeline. HDD is used as a method to install product pipes for water, sewer, gas, storm-water culverts, electrical cables, optic fibre, drainage, sleeves for future development, etc.

What makes HDD unique and superior to other forms of new pipeline installation is that we can guide our drill head and can drill to a specified grade to allow the installed line to have a fall over 2 points. Excavations are far less when compared to open trenching as we generally only require a launch and reception pit. HDD reduces disruption to traffic as we can generally operate outside of the road reserve.

Where can HDD be used?

HDD is commonly used for drilling under rivers, roadways, highways, bridges, railways, wetlands, etc. each crossing has its own unique challenges from interference from the surrounding area to challenging ground conditions where only experience can ensure that the crossing has the best chance of success.

Our Capabilities

We have the necessary tooling for drilling in ground conditions that range from soft drillable material, intermediate drillable material, hard drillable material as well as rock. Our rock hammer is a Straightline Rock Eye air hammer, regarded as one of the best air hammers in the industry, and has been imported from the USA.

Our comprehensive range of HDD rigs allows us to drill and install pipelines from a 25mm diameter pipe up to an 800mm diameter pipe, this is dependent on the ground conditions as well as the length of the crossing.

We have tooling to ream up to a 600mm hole in solid rock with our range of hole openers and back hammers.

Our flagship HDD rig, the American Auger DD-10 has a pull-back capacity of 45 metric tons and is capable of drilling up to 1000 meters depending on the size of the pipe to be installed and the nature of the ground conditions.

We have a Group 33 Engineering designed and manufactured HDD pit machine that allows us to complete crossings where available site space is restricted, we are in the process of designing an HDD pit machine that is capable of drilling in Hard Rock.

A quick run-through of the HDD Process

The HDD process is initiated by the HDD rig standing at ground level, or if the pit machine is used from within the pit. The first step is known as the pilot hole/bore and is the most crucial step of the HDD process as the rest of the drill will follow this bore path. The HDD operator together with an HDD assistant who walks at the ground level to track the inclination, depth, and direction of the drill head. This information is then relayed to a screen at the operators’ controls. The HDD operator uses this information to guide the HDD head according to the specific requirements as set out by the client/designers.

Once the pilot hole is completed the back reaming stage commences, the back reaming is done in stages, this is to open the pilot hole/bore to the desired diameter where the product pipe will be installed, the stages and tooling used will be dependent on the ground conditions, diameter of the desired product pipe and the length of the crossing. Once the back reaming is completed the new product pipe is then installed.

In most cases our final reamer will have a larger diameter than the product pipe to be installed, thus there will be an annular void which the client may decide to grout depending on the cover above the annular void.

Throughout the HDD process, a mud mix is used, this is to ensure that the bore's integrity is maintained, the mud mix is also used as a medium to allow all the cuttings and excess soil to be moved out of the bore and into a pit. Lastly, the mud mix ensures that there is reduced skin friction between the product pipe and the bore. Depending on the ground conditions of the bore different mud mix chemicals are used or a combination of mud mix chemicals are used.

We only use industry-leading additives for our mud mixes, which pose no significant environmental risks.