Horizontal directional drilling (HDD) is one of the contemporary methods of trenchless (closed) pipe laying (click here) . These methods of trenchless engineering are the most advanced technologies and most promising from an economic point of view.
The most common of these are:
- Stamping steel cases;
- Auger Drilling;
- Micro tunneling;
- Horizontal directional drilling.
Stamping of steel cases is made by special hydraulic jacks, which push the pipe (case) into the ground removing the soil from the pipe, leaving it as a case. This process time consuming, but its advantage is the possibility of laying metal cases of large diameter – from 800 mm or more; at a distance of not more than 80 meters. However, with smaller diameters and larger lengths this method of trenchless laying is not effective.
Auger drilling is a relatively cheap technology for laying pipelines using screw drilling machines. Drilling is performed between two excavations, which must be excavated and prepared.
Microtunneling is a trenchless method of constructing reservoirs, while the laying of pipes in the ground is performed by a tunneling micro-board. Its forward movement is provided by a powerful jack-house station, which transmits the pushing force to the shield through a column of reinforced concrete pipes, which is built up as it moves forward – between two pits located at a distance of up to 500 meters from each other. The main advantage of this method of underground communication laying is a large diameter – up to several meters.
Horizontal directional drilling is the most universal and widespread method of trenchless laying engineering with the help of special drilling rigs, developed in 1971 by the American engineer Martin Cherrington.
Unlike other trenchless methods, this technology allows the laying of polyethylene, steel and cast iron pipes with a diameter from 63 mm to 1000 mm, at a depth of 1 to 25 meters. The length of the trenchless underground section depends on the diameter of the pipe being laid and the equipment’s capacity, and at the same time it can reach 2000 meters.
The widely used horizontal drilling in recent times catalyzes the process, reducing time and labor costs especially in the construction of underground pipelines under natural obstacles (rivers, ravines, lakes, forests, quicksands) and in urban conditions (railways, tracks, squares, parks, etc.) .
In general, horizontal directional drilling is used for laying pipelines, sewerage, water pipes, gas pipelines and cases for communication cables without tampering with ground surface, while preserving the natural landscape.
It should be noted that a puncture under the road is the only way to lay additional communications without excavating a traditional trench.
Horizontal Directional Drilling Technology
The first stage of horizontal drilling is the drilling of a pilot well, carried out with the help of a drill bit with a bevel in the front and an integrated transmitter. The location information and the angle of the drill head inclination is transmitted to the location system monitor. Through special holes in the drill bit, bentonite drilling mud is applied, which reduces friction and protects the well from falling. The first stage is completed as soon as the drill head comes out at the projected point in accordance with the design profile.
The second stage is the expansion of the borehole diameter with the help of a reverse action expand or a rimmer. For the further unhindered extension of communications, it is necessary to increase the well so that its diameter exceeds by 25-30% the diameter of the pipeline.
At the final stage, the pipeline itself is stretched, to the front end of which the headband is attached with the swinging force and the rimmer taking the pulling force. Thus, the drilling rig pulls the pipeline through a predetermined trajectory (click here).
Horizontal directional drilling rigs have different capacities up to 500 tons – depending on the weight of the pipeline that needs to be laid underground. The more powerful the installation, the longer the drill-hole must be made. However, the installation must be selected for the type of work to be performed, since it is not rational to pull a pipe 110 mm in diameter by a distance of 10 meters by a force of 500 tons. It is expensive.
Due to the use of horizontal directional drilling technology, it is possible to make underground junctions of varying complexity regardless of natural obstacles, weather or season. The equipment has ultra-high accuracy reducing the possibility of damage to other paved utility networks. The punctures carried out are safe for the environment and do not lead to the destruction of the landscape.
Among the advantages is a reduction in the operating time, regardless of the natural obstacles at site; extended service life of the laid pipelines and communications; reduction of financial costs to 30%; no distortion to vehicular traffic, road surface preservation, and so on.
Unlike other types of underground laying, there is no need to build trenches or weld a pipe in an underground pit – in the course of its punching or pushing or have a number of other inconveniences. Horizontal directional drilling machines come to the site and quickly get the work done even on unprepared sites.
That is why trench-less technology for laying pipes, pipelines and communications is economically beneficial, most effective and in some cases simply irreplaceable.