Construction of Germany’s second longest Motorway Tunnel: The Hirschhagen Tunnel
The construction of the A 44 motorway between Kassel and Herleshausen is an important part of the trans-European motorway network. After its completion, the A 44 will efficiently connect the Benelux States in the West and Poland in the East.
In the section between Kassel and Herleshausen, the construction of the Hirschhagen Tunnel was necessary because of the local topography. The tunnel is designed as a double tube tunnel with 2 lanes each. The tunnel tubes are connected with each other by cross passages. The northern tunnel tube has a length of 4,128m, and the southern tube has a total length of 4,187m. After its completion, the Hirschhagen Tunnel will be Germany’s second longest motorway tunnel.
The tunnel portals are being built using open cut tunneling. Tied-back bored pile walls and a sheeting wall system are used for stabilizing the excavation at the western portal. Additionally, a vertical end wall with lateral retaining walls is being built in this area.
The cover above the crown measures up to 80m deep. Both tubes are being built using conventional tunneling methods and run mainly through colored sandstone formations. Tunneling is proceeding simultaneously from both tunnel portals.
The undercrossing of the Losse River near Eschenstruth is especially difficult. Underneath the river, there is a porous mixture of clay and sand deposits that is saturated. For undercrossing the river, an approx. 300m long gallery is being built at a depth of 15m through which the water will be drained from the surrounding ground.
The tubes are ventilated via a more than 80m deep shaft, the inner lining of which will be resistant to pressurized water and fitted with single-layer waterproofing.
DSI produced and supplied the AT – 139 Pipe Umbrella System for the construction of the two tunnel tubes. The system is especially suitable for tunneling in soft ground that is prone to subsidence and has the following principal advantages:
- Fast self-drilling installation
- Smallest possible stress relaxation due to an immediate support of the borehole wall during installation
- Accurate installation due to a minimized annular gap
In this project, a newly developed squeezed connection by DSI was used for the first time for the fast and safe connection of the casing tubes. This new squeezed connection is an important milestone in the history of the AT – Pipe Umbrella System that ensures an easy and cost-efficient connection of casing tubes on site.
In addition, DSI supplied numerous ground support products such as SN Anchors, DYWI® Drill Hollow Bar Anchors as well as the AT – TUBESPILE™ and DYWI® Drill Self-Drilling Spiles for pre-support.