Successful application at the Jagdberg Tunnel

Jähnig GmbH, a company based in Dorfhain near Dresden, was contracted to work on stabilizing the embankments at the western and eastern tunnel portals of the Jagdberg Tunnel. The new A4 motorway section of around 10 km in length and the renaturation of the old motorway section will facilitate the EU’s Eastern European expansion and benefit nature in the “Leutratal” region. As part of this € 300 mill. project, 3.8 mill. m³ of excavated material and earth will be moved and, at the eastern portal alone, 118 404 m drilled for the anchors and drainage. With its supervision of the foundation engineering at the Jagdberg Tunnel, Jähnig is increasing its lead in this type of retaining work. Scrutiny of the call for tender already revealed that the geology at the Jagdberg Tunnel is different and any work there must be classified as difficult. At the eastern portal, the underground is predominantly rocky, consisting of shell limestone, at the western portal various fault zones are encountered. On account of this geological profile, drilling and suitable anchors from 7 to 16 m are necessary.

In the selection of the required technology, the Sandvik DQ500 with 180 ° rotating superstructure proved the ideal drilling rig for the work necessary. Jähnig chose the model with operator cabin so as to ensure the safety of the operatives and protect their health. Increasing angles of 3 to 5 ° for the drainage drilling and decreasing angles of around 20° for the anchor drilling are no problem for the rig. Work on the western portal began in June 2008. Work on the eastern portal is to be completed by December 2010. Since January 2010, 470 m will be drilled daily with the DQ500 series (Fig.) With this high work rate, the prescribed maintenance intervals must be efficiently coordinated. Moreover every drilled hole is documented. Date, kilometres covered, drilling time, drilling depth and remarks for each of the total 11 160 boreholes are recorded in the log.

On account of the difficult geology and the weather conditions, Jähnig also subcontracted the company Jens Weiss. This company uses the same drilling rig, but the DQ500R model without a cabin, but with radio control for better positioning and set-up. 

Sandvik Mining and Construction Central Europe GmbH, Essen (D), Olaf Gruner, Tel.: +49 172 2058 468, E-Mail: olaf.gruner@sandvik.com, www.sandvik.com