Hopfenberg Tunnel

The Hopfenberg Tunnel was set up to the south of Hessisch Lichtenau as part of the new BAB44 Kassel-Herleshausen motorway scheme. The new BAB 44 route represents an element of the German Unity - Road Transport project. The Hopfenberg Tunnel consists of 2 separate drives set up roughly 29 m apart. The 2 tubes deviate from Kassel towards Herleshausen to the left with a radius of 1,015 m in the northern bare and a radius of 1,030 m in the southern one. Both drop by a gradient varying between 1.9 and 2.81 % towards Herleshausen. The selected tunnel cross-section is a RQ 26 t. The clearance width consists of 2 lanes (each 3.50 m), the verge strips (0.25 m) and the emergency footpaths (each 1.00 m). The clearance height amounts to 4.50 m. A cross-passage approx. 16.5 m in length with an incline of 2.6 % towards the northern tube is located in the middle of the tunnel. The maximum overburden amounts to approx.25 m - starting with around 3 m in the pre-cut zone. The tunnel was driven starting from the east in Lower Keuper, series of rock from alternating marine and terrestrial deposits. As a result, by and large, interbedded strata consisting of not particularly solid clay and marl rocks and hard limestone layers were encountered, with high strength sandstones as channel fills present locally. Towards the west, limestones belonging to the Upper Shell Lime formation were penetrated within the course of a fault. The route actually follows a tectonic fault system. This accounts for the fact that the rocks are increasingly interstratified by parting planes and are partially extremely loosened and weathered. Based on the prevailing geological conditions a NATM drive was selected to excavate the tunnel. The overall cross-section was excavated in 3 part-sections (crown, bench and partial base invert).The rock was mainly loosened by means of gentle blasting. A few part-sections were tackled by an excavator with blasting designed to loosen the rock. The excavated material was reutilised for filling purposes. Supporting was carried out using steel arches and reinforced shotcrete, a rock bolt system and advance lances. The greatest part of the tunnel was provided with an open cross-section. A base invert was installed in a short part-section. A joint tunnel operational centre was built in front of the eastern abutment of the Hopfenbachtal Bridge for the Hopfenbach Tunnel and the approx. 550 m distant Walberg Tunnel. In front of the portals, crossings were set up and an extinguishing water basin with pressure boosting system produced at the west portal. A recovery pond is installed at the Hopfenberg Tunnel's east portal. A 7 m high ventilation dividing wall was erected in the west portal's access and exit area.

Country: Germany
Region: Hessen
Tunnel utilization: Traffic
Type of utilization: Road tunnel
Client: Federal Republic of Germany - Land Hessen
Consulting Engineer: Bung Beratende Ingenieure
Construction monitoring: Bung Beratende Ingenieure, Müller + Hereth GmbH
Contractor: Ed. Züblin AG, Alpine Bau Deutschland GmbH, Bickardt-Bau AG, Gebr. Bommart GmbH & Co. KG
Main construction method: Trenchless
Type of excavation: Drill-and-blast/Excavator
Lining: Concrete formwork
No. of tubes: 2
Tunnel total length: northern bare 543 m, 457 m of which was driven by trenchless means southern bore 539 m, 453 m of which was driven by trenchless means
Cross-section: 95 - 106 m²
Contract Volume: roughwork approx. € 19 million, technical furnishings approx. € 3 million
Construction start/end: March 2002 - August 2005
Opening: September 2005