Horizontal Directional Drilling, often known as HDD, is a trenchless technique of placing underground conduit, pipe, or cable in a shallow arc following a predetermined bore route utilising a piece of surface-launched drilling equipment with minimum effect on the surrounding region.
When trenching or excavation is impractical, directional drilling is employed. It is appropriate for various soil types and tasks, such as roads, river crossings, and landscapes. A pipe may be built of any material dragged through the drilled hole, including PVC, polyethene, steel, polypropylene, and ductile iron.
Read this article to find out more about utility HDD.
What Exactly Is HDD?
HDD has gone a long way since its introduction to the trenchless construction landscape in the 1970s. It provides a curved trajectory rather than point-to-point answers in a straight line. As a result, HDD made it possible to place pipes in utilities under roadways, trains, rivers, and crowded locations.
HDD technology is still evolving, with innovations in steering and mud systems playing a role in expanding the adoption of this trenchless approach.
How Does Horizontal Directional Drilling Work?
By drilling a hole following the desired trajectory, HDD installed underground pipelines or services. Drilling the pilot hole, riveting and installing the casing, and bringing the pipe into place are generally the three required processes. This process has minor changes based on the project’s needs, but this is how most HDD instals are done.
Required Equipment for Horizontal Directional Drilling
The drilling rig is the most important component of an HDD mining arrangement. While the drilling head moves through the earth, drilling rods are inserted one segment at a time. A drilling head connected to the drill string’s front cuts through the dirt and deposits the cuttings in the tunnel. There are several drilling heads for various ground types.
The majority of HDD projects depend on a drilling mud system. This bentonite mixture covers the tunnel walls and keeps them from sinking (settling or sinking). It also transports the cuttings out of the tunnel and lubricates and cools the drilling head.
The first step in a utility HDD project is to drill a pilot bore. The pilot bore’s function is to check that the pipe follows the specified trajectory. The pilot hole is relatively shallow and easy to drill, enabling contractors to identify any concerns with the ground condition before pulling the pipe into place.
The second step is to ream the pilot bore and expand the bore size to accommodate the product pipe. Reaming may need numerous passes, each larger than the previous one until the ultimate size is obtained. A reaming tool is attached to the end of the drill string instead of the drilling head. Drilling mud is essential for extracting cuttings from the tunnel and preserving the wall’s stability.
The third step in utility HDD is pipe laying. At the front of the drill string, a pulling head and swivel replace the drilling head. Piping is frequently pushed back into the bore from the destination location, which requires a lot of energy and puts a lot of strain on the pipe. A stuck pipe is one of the issues that might arise here, as the pipe refuses to advance any farther down the tunnel.
The Limitations of Horizontal Directional Drilling
The majority of HDD’s drawbacks are connected to the usage of drilling mud and ground conditions. Certain ground conditions feature loose gravel or dirt, which makes sealing the bore problematic. In these circumstances, installing a casing, followed by the product pipe, may be preferable.
Because of strong pressure or inappropriate drilling mud composition, drilling mud may explode from the tube onto the surrounding earth. This failure may result in subsidence and environmental damage, causing project delays while the problem is resolved.
The Benefits of Horizontal Directional Drilling
Exit and entrance trenches are not required for HDD installations. The piping is put at an angle into the earth from the surface. This method removes the need for exit and entrance pits, although it may still need a substantial footprint for pipe run-up into the hole.
The capacity to track curved trajectories is a key advantage of utility HDD. Traditional trenchless building technologies, such as auger drilling, can only go in a straight path. Curved trajectories enable pipes to descend under a river, train line, or road and then rise on the other side. There are no subsurface elbows or right-angle alterations in the flow pattern to be concerned about. The invention of the HDPE pipe has also contributed to this advantage since, unlike steel piping, it is flexible enough to follow a curved trajectory.
HDD is a flexible and well-known trenchless building technique. It is particularly suited to curving courses under rivers and other obstructions.
Drilling mud systems are critical to the success of utility HDD installations and must be carefully designed and engineered as a component of project planning. HDD steering technology advancements also enhance the precision of HDD instals compared to the steering choices available when the technique was initially introduced.