Two years after successful demonstration of its award-winning Pipe Express semi-trenchless system at bauma2013, Herrenknecht completes the third successful field demonstration of the technology in Sweden.
Some 10km south of Stockholm, and using the rapid Pipe Express system, Züblin Scandinavia AB has installed a 48in diameter water pipeline of 1,035m in length within just 12 days. About 60 percent of this time was taken up welding and coating the 224m long steel pipe strings, rather than driving the excavation.
Groundwater lowering was not required despite the high water level in the saturated clay geology. Compared to conventional open-cut construction the method developed by Herrenknecht has significantly less impact on the environment, reduces trench width excavation by up to 70%, while substantially minimising costs.
“For open-cut construction we would have needed sheet piles, and that would have meant lowering the groundwater,” said Mats Ohlsson, Project Manager for the client, Stockholm Vatten. In the most productive 12-hour shift, 221m of pipeline was installed, and over the duration of the project an average construction performance of 0.7m/minute was achieved.
Michael Lubberger, Senior Pipeline Product Manager at Herrenknecht, said: “Following a pilot project in the Netherlands, and the subsequent deployment of the Pipe Express system in Thailand, this was our third drive. We see strong potential for the new method on the pipeline market and the keen interest of international specialists at the jobsite confirms this view.”
Pipe Express is a semi-trenchless near-surface pipeline installation method in which a milling unit with a trenching system creates a narrow, approximately 40cm wide trench on the surface. Below the surface unit, and under the ground, a micro TBM machine is attached to excavate the tunnel, which can be up to 1.5m in diameter.
Rather than being extracted in the traditional manner from behind the machine, the excavated soil is brought to the surface by the trenching unit and used to simultaneously backfill the trench behind the machine as it and the TBM below advance. The driving force for both excavation unit and pipeline insertion behind the micro TBM is provided by a Herrenknecht Pipe Thruster located at the starting position.
In contrast to the conventional construction method the trenches, including construction paths, are up to 70 percent narrower. Extensive earthworks, groundwater lowering, and the ramming of sheet piles is not necessary. Up to 2,000m long pipelines with a diameter of 900–1,500mm (36–60in) can be laid quickly and cost-efficiently, and to depths of up to 2.5m, using the Pipe Express system.
It is estimated that the global demand for below-ground pipeline installation for the oil, gas and water industries is currently running at 25,000km/year.