Herrenknecht’s newly developed semi-trenchless method for pipeline installation has completed its third successful mission. South of Stockholm, Züblin Scandinavia AB installed a water pipeline more than a kilometer in length within 12 days using Pipe Express. Groundwater lowering was not required despite a water level just below the terrain’s surface. Compared to conventional open-cut construction the method has significantly less impact on the environment, while simultaneously minimizing costs.
The benefits were obvious to Mats Ohlsson, project manager of client Stockholm Vatten: “For open-cut construction we would have needed sheet piles and we would have had to lower the groundwater.” The Pipe Express method from Herrenknecht, however, requires no lowering of the groundwater. The construction company made the most of this enormous budget and time advantage. It used Pipe Express for the laying of a 1,036-m section of a 48-in. water pipeline near Huddinge, some 10 km south of Stockholm. Drilling started on Feb. 22, 2015, and the destination reached on March 5. In the most productive 12-hour shift, 221 m of pipeline disappeared into the ground; the average construction performance was 0.70 m per minute. About 60 percent of the construction time was taken up just with welding and coating the up to 224-m long steel pipe strings.
Michael Lubberger, Senior Product Manager for Pipelines at Herrenknecht, is proud of the success in Sweden: “After the pilot project in the Netherlands and the subsequent deployment in Thailand, this is already our third drive with Pipe Express. We see strong potential for the new method on the pipeline market.” The keen interest of international specialists on the site confirms this view.
Pipe Express from Herrenknecht is a new, semi-trenchless near-surface pipeline installation method. In this method, a buggy with a trenching unit creates a narrow, approximately 40 cm wide trench on the surface. Below it in the soil a boring machine is mounted that digs the actual tunnel with diameters of up to 1.5 m and lays the pipeline at the same time. The excavated soil is brought to the surface by the trenching unit and backfilled in the trench again behind the machine; laborious finishing work is not required. The pushing force for both excavation unit and pipeline is provided by a Herrenknecht Pipe Thruster located at the starting position.
In contrast to the conventional construction method, the corridors, including construction paths, are up to 70 percent narrower. Extensive earthworks, groundwater lowering, the ramming of sheet piles, etc., are not necessary. Up to 2,000-m long pipelines with a diameter of 900 to 1,500 mm (36 to 60 in.) can thus be laid quickly and cost-efficiently.
The company Stockholm Vatten produces around 370,000 cubic m of drinking water daily for the 1.3 million residents of the Swedish capital. Züblin Scandinavia AB were contracted to add one kilometer of pipeline south of Stockholm to the existing network.