Highspeed Trenchless Installation of Pipes and Cables in Open Terrains

Dr. Ing. Hubert Müller, Frank Föckersperger GmbH
Special Collaboration

Application of modern plowing technology results in time and cost savings on construction projects

Especially in rural areas open trench installation is needlessly laborious and often not cost effective. Since 1971, manufacturing company Frank Föckersperger GmbH from Aurachtal in Germany has offered a fundamental new development in installation methods which has been continuously advanced and improved ever since. The technique is the so-called “Pipe and Cable Plow” technique. By using a cable-pulled special plow system, pipes and cables are buried directly into the ground. The technique offers a way to place power and broadband cables over long distances as well as water and gas pipes up to Ø 355 mm (in soft soils up to Ø 450 mm).

The plowing technique has been shown to be exceptionally efficient, time saving and environmentally-sound as no trenches have to be dug with only the plow trace having to be evened out. Daily performance (meters installed) with a plowing unit can exceed 5,000 m with only a small start and construction pit being required for setting up and aligning the plow. The pulling winch, having a pulling force up to 160 t with a winch rope of up to 130 m length, is mounted on an all-terrain vehicle and applies tension automatically at the target point. The plow unit with the plow blade is mounted on a specially designed tire-mounted vehicle with hydraulic height and track gauge adjustment functions. These functions enable application of the system even on uneven terrain and for crossing beneath small water obstacles. The plow blade is precisely hydraulically adjustable in height so that the plowing/installation depth can be adapted steplessly to the ground conditions encountered.

The most spectacular application made so far using the “Pipe and Cable Plow” was the installation of a 5 km-long water pipeline through mud flats on the North Sea coast, in Germany, to provide drinking water facilities for the 1,200 inhabitants of the island of Pellworm. ( http://www.infrastructures.com/0704/tracto.htm )

Unlike the “Pipe and Cable Plow”, the Rocket Plow® (designed and patented by Frank Föckersperger) has the pipe mounted directly to the expansion body (rocket) so it can be pulled into the void this rocket is generating. The expansion body establishes voids reaching a maximal size of 500 mm in diameter. Therefore, PE pipes up to Ø 355 mm and cast iron pipes (cement-mortar coating) up to Ø 200 mm can be pulled in. With the help of the chute mounted to the expansion body, additional cables and warning tapes can be installed. The 300 m-long pipe string is laid out behind the launch pit and pulled in by the Rocket Plow. The tractive forces affecting the pipe are monitored using a measuring device.

An impressive example of the Rocket Plow’s capabilities was the installation of a new drinking water pipeline on behalf of the water authorities of Bautzen between the communities of Bornitz and Radibor in Germany. The pipeline Ø 315 mm SDR 11 was installed in single sections of approx 250 m length, consisting of 12 m long pipe segments which were butt-welded together on site, The first section was pulled in in only 32 minutes, pulling in of the complete pipeline over 1,000 m length took only 8 hours altogether.

The soil-mechanics processes that occur during plowing have been examined as part of a government-funded research-project with participation of the University of the Federal Armed Forces in Neubiberg, Germany; the engineering office Stein & Partner and Frank Föckersperger GmbH, manufacturer of the plowing system. These tests showed that pipes and cables are subjected to less strain when plowed into the ground than when using common open trench methods, as the soil is subjected to minimum interference during the installation process.

The plowing technique can be applied in non-cohesive and cohesive loose soils. Since 1971 the company Frank Föckersperger has successfully plowed in some 70,000 km of pipes and cables. This degree of experience, as well as the theoretical and experimental research that has been undertaken over the past 40 years, has firmly established the viability of the technique.

Since 2003 the plowing technique has been accepted in the respective German ATV and DVGW standards which regulate application range, requirements and quality control.

This now means that a highly economic, environmentally sound and versatile technique, which guarantees minimal interference of the soil, is available to users and contractors.

Föckersperger developes and manufactures the machine technology solely in-house. Within Germany, five different plow systems are provided as a service including operating personnel. Outside of Germany the plows are sold to civil engineering companies.

Source: Frank Föckersperger GmbH

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