technology. Using this method, the surface of landscape remains intact, including beautification features, roadway, building and constructions. Currently several proven techniques of horizontal directional drilling are developed and frequently used in order to reduce the costs of communications laying and preservation of the objects above the ground.
Horizontal directional drilling
When using the HDD method, the cost of similar works can be reduced by 2-3 times. If it is not possible to lay communications on the landscape on traditional way, the soil puncturing method is applied.
The method of horizontal directional drilling is used for various purposes:
- Laying of pipelines, gas lines, electric cables and other communication lines for buildings.
- Formation of wells for oil and minerals extraction.
- Replacement of old communications and equipment.
- Arrangement of underground highways.
Besides the demand for technology, HDD provides certain advantages:
- Destructions on the surface are minimized (it is needed to dig only 2 basins).
- It is required a small team of 3-5 people to carry out the work.
- The equipment for drilling is mobile, it is easily delivered and installed at the work site.
- HDD method allows to equip communications more quickly and cheaper, so that the technology has gained a huge popularity everywhere.
General description of the technology
Horizontal Directional Drilling is based on using the drilling equipment. The general technology of puncturing comes to the following manipulations:
- Project documentation with calculations is prepared for accurate horizontal drilling in the soil.
- The projects are compliant with local authority and landowners.
- Two basins are digged out at the site of works start and communications exit in the location, where the drilling will take place.
- Laying of necessary pipelines are carried out with the help of drilling tools.
- Completion of work, removal of basins, restoration of sites at their location if necessary.
The above description is brief, currently several types of HDD have been developed. The application of a certain type of horizontal drilling is carried out depending on the soil type, laying communication lines and other factors.
Stages of HDD works
Drilling process demands an attentive attitude, control and adherence to technological characteristics at every step.
Before underground communications laying, the landscape and equipment must be prepared:
- Site development for the drilling machine is of universal size, 10х15m.
- If necessary, provide a detour road for the machine.
- Set down the drilling equipment in appropriate place of the pilot boring launch.
- Fix all necessary systems before the operation.
- Adjust all necessary drilling tools.
- Adjust the radio communication between team members.
- If it’s necessary, built an additional lead for bentonite liquid and groundwater.
At the preparation stage, in order to bring any harm to the existing pipelines it is important to calculate the location of them. It is also necessary to have the 10 m distance between the main machine and mud mixing system.
It is also very important to explore the soil of project and choose the appropriate drill bits and reamers before pilot drilling. The whole drilling object must be protected with a yellow warning tape.
After finishing the preparatory work, the next stage is drilling process:
Pilot boring requirements:
- The diameter of pilot boring is 10 cm.
- Adjusting drill bit by 10 – 20 ° relative to the horizon line;
- Pilot boring path is checking every 3 meters’ length.
Backreaming process requirements:
- Expansion of the pilot hole: the drill bit is removed and replaced by an appropriate reamer;
- Full extension of the reamer through the formed channel with constant correction of movement.
It is necessary to use a drilling mud during whole drilling process. The drilling mud must have sufficient gel strength to keep cuttings suspended for transport, to form a filter cake on the borehole wall that contains the water within the drilling fluid, and to provide lubrication between the pipe and the borehole on pullback.
It is important to consider the possibility of soil caving. In order to exclude the violation of the technology, it is necessary to connect all parts of the pipes with each other reliably.
Advantages and disadvantages of HDD technology
Horizontal directional drilling was invented in 1960. From then on, the HDD has been actively used all over the world. Like any other technologies, the HDD has its advantages and disadvantages
- Less waste of resources, finance, labor and time
- Costs for laying communications are reduced due to the lack of the need to restore the environment;
- You can work in any areas, including historical places, high-voltage stations, unfavorable climatic conditions;
- The soil structure is preserved; the fertile soil layers are not disturbed;
- The usual urban rhythm is also not disturbed, there is no need to stop the road traffic.
- If it is necessary to lay a pipeline of high length or at great depth, the trenchless method is more expensive.