Direct Pipe technology

Direct Pipe® technology combines the advantages of microtunnelling and HDD technology. In one step only, a prefabricated pipeline can be installed and the required borehole excavated at the same time. This allows speedy and highly economic installation of pipelines with lengths of more than 1,500 meters.

The well is formed by drilling, removal by pumps of the drilled rock through transport communications located inside the shield and pipeline. Well formation by drilling and pipeline pushing are synchronized with each other.

Rock drilling is carried out by cutting heads of 3 types, depending on the geological structure and category of soils (sands, clays, limestones, gravel, rocks), water and drilling mud are fed into the face through feeding communications located inside the shield and pipeline.

Water and bentonite-based drilling mud are used to wash out the rock, remove the drilled rock and fill the pipe space. The annular space in the well is filled with bentonite solution, which provides lubrication and reduces friction during punching.

In case of wear of the cutting bodies, it is possible to replace the cutting tool by removing the shield and the pipeline in reverse with the help of a pusher and then laying the pipeline along the same trajectory.

Reverse extraction is possible if there is a distance that allows you to place the extracted lash of the pipeline without undocking.

In cramped conditions, with a limited distance of placement of the pipeline whip, it is possible to work with short sections of the pipeline, welding short sections during sinking and punching.

At the end of the sinking, the shield goes to the specified mark (ground surface, pit), the shield and the pipeline are undocked, the supply and transport communications are removed from the pipeline, the rail tracks are dismantled, along which the working personnel move, if necessary, repair.

This technology allows you to safely work with all types of insulation (polyethylene, polypropylene, fiberglass, epoxy coating, concrete coating), the thickness of the insulation coating is determined by the project.

It should be noted that the two main components of the tunnel equipment are the AVN tunneling machine used for microtunneling and the pipe pusher used for NNB (directional drilling) they are used by specialized enterprises, which allows companies, after a minor modernization, to expand their technological capabilities and implement various methods of construction of underwater crossings (NNB, microtunneling and Direct Pipe).

Areas of application of Direct Pipe technology

• Underwater crossings through rivers and channels, exits to the sea, crossings over hills and mountains, crossings under archaeological and specially protected areas, roads and railways in complicated geological conditions, in which the use of NNB technology is limited due to the distance of penetration, the diameter of the pipeline or when the use of microtunneling technology is limited by the construction time, complex logistics conditions for the supply of iron-concrete pipes, cost indicators.
• Pipe diameters: from 30”/762mm to 60”/1520mm.
• Length of penetration: depends on the diameter, geology, the possibility of replacing the cutting tool with a "reverse stroke" or in intermediate pits, etc.
• Driving record: 1,930 m (48 " pipeline).

Main advantages of Direct Pipe

• The installation of the pipeline in one step
• Minimization of geological risks
• Possibility of dividing into several sections of pipes
• Minimized environmental risks
• The reduced diameter bore
• One-way spatial requirements for seawater outlets and coastal approaches
• Simple entrance and exit pits.