Stockholm / Schwanau, April 8, 2015. 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 meter long section of a 48-inch water pipeline near Huddinge, some 10 kilometers south of Stockholm. After drilling started on February 22, on March 5, 2015 already the destination had been reached. In the most productive 12-hour shift, 221 meters of pipeline disappeared into the ground; the average construction performance was 0.70 meters per minute. About 60 percent of the construction time was taken up just with welding and coating the up to 224 meter long steel pipe strings.
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 centimeter 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 1.50 meters 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 meter long pipelines with a diameter of 900 – 1,500 millimeters (36" - 60") can thus be laid quickly and cost-efficiently.
The company Stockholm Vatten produces around 370,000 m³ 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.