In Northern Germany, the existing pipeline network is being modernized for regional gas supply. This major project also includes the “Elbedüker Hetlingen” where a Herrenknecht AVND machine (Ø 3,025 mm) crossed under the Elbe near Hamburg in the second half of 2014.
The tunnel was driven in a pipe-jacking process from the town of Hetlingen to the target shaft on Lühesand Island on the Elbe – under high pressure in terms of both time and water. “Construction of the two new gas transit pipelines enables us to guarantee gas supplies for Northern Germany and Scandinavia also in the future,” said Dr. Philipp v. Bergmann-Korn, spokesman for the client Gasunie Deutschland Services GmbH.
Even before the project start, everyone involved was aware of the huge technical challenges associated with the construction. The diversified ground ranged from sandy gravel soil with stones through layers of boulder clay featuring larger rocks to layers of clay which tend to be very sticky. This was exacerbated by high water pressures of up to 4 bar as well as a route length of more than 1.5 kilometers (0.93 miles), making the project one of the longest pipe-jacking jobs in the world. In its capacity as drilling company, A.Hak Drillcon relied on the expertise and support offered by Herrenknecht right from the start. Even during refurbishment and project-specific modification of the used AVND2400AB, collaboration was hand-in-hand and included a videoscope examination of the main bearing as well as adaptation of the manlock and the main bearing sealing for water pressures of up to 4 bar.