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Hahnenkamp Tunnel, BAB A30

1 General

1.1 Task definition

The northern freeway bypass of Bad Oeynhausen closes a gap in the trunk road network of the BAB A 30/A 2 between the freeway interchange Löhne and the freeway interchange Rehme and thus relieves the inner-city traffic on the B 61 in Bad Oeynhausen (up to 50,000 motor vehicles/d). The section completes the east-west axis from the Netherlands to Berlin. The 9.S km long bypass section was built in four construction phases and includes 26 bridges as well as the Hahnenkamp tunnel following construction phase 2. The construction of the tunnel was necessary to ensure noise protection for the Hahnenkamp district.

1.2 Road design

The route in the area of the tunnel structure and the adjacent trough structures on both sides is located in a green corridor of the Hahnenkamp district and passes under Dehmer Strasse (B 61alt) and a local road. The terrain runs in a natural gradient from north to south. The bridge over the Werre River directly adjoins the trough south. The axis runs from north to south first in a turning clothoid with the parameters A = 320 and A = 467 and lies in a left-hand curve with a radius of R = 1400 m in the further course of the tunnel. In longitudinal section, the northern trough structure is located in a rounded hilltop, where the gradient changes from a 0.4 % slope to a 2.8 % gradient in a southerly direction. The southern trough structure is located in a trough rounding of the gradient, changing from 2.8% gradient to 0.585% gradient. In the tunnel area, the road cross-section RQ 26 t was designed in accordance with the guidelines for equipping and operating road tunnels. The two tunnel cells each contain two lanes with a width of 350 m, 0.50 m wide verges and 1.00 m wide emergency walkways on both sides. This results in a minimum clear width of 10.00 m for each tunnel cell. Due to the height of the clearance profile, which is set at 4.70 m, and an extended clearance for fixtures, the total height between the roadway and the tunnel roof is 5.14 m. The tunnel is thus not only a very high roadway, but also a very low roadway. The road cross-section RQ 26 T is decisive for the troughs. Both trough cells contain two traffic lanes, each 3.50 m wide, 0.50 m wide shoulder strips as well as a side strip of 2.00 m each and emergency walkways on both sides, each 1.00 m wide. This results in a minimum clear width of 12.00 m for each trough cell. The carriageways are designed with a transverse gradient varying between 2.5% and 3.0%.

1.3 Structure design

In accordance with the boundary conditions from the road planning and the soil survey, a two-cell trough/tunnel structure was selected as a water-impermeable concrete structure in accordance with ZTV-ING, Part 2. The structure has a shallow foundation, and the component thicknesses were determined according to structural requirements, but in particular according to the requirements of buoyancy control. In addition, the tunnel section has been provided with an approx. 1.00 m high backfill to ensure buoyancy control. With this backfill, the required safety against uplift can be ensured for the final state. For temporary construction conditions (e.g. excavations above the tunnel), buoyancy safety is ensured solely by the dead weight of the structure. The length of the tunnel section is 450 m. The trough lengths were determined according to the criterion that the design water level at the ends of the trough should be 1.00 m below grade. This resulted in a length of 178 m for the northern trough and 138 m for the southern trough. The upper edges of the trough walls are again at least 0.50 m above the design groundwater level. Noise protection elements with an absorption layer of aerated concrete were installed on the walls of the troughs, and aluminum cassettes were used to extend the noise protection up to 30 m into the tunnel. The noise protection elements were designed according to the color concept. In order to reduce the lighting effort in the entrance and exit areas of the tunnel, RAL 7030 was chosen as the lightest color for the upper elements over a length of approx. 100 m. The color of the upper elements was also chosen as the lightest color in the tunnel. The element color then gradually darkens inward. The portals were designed on the basis of the design concept of the working group Dr.-lng. Kind-Barkauskas, Henry Ripke Architekten and VIC Potsdam. They will be designed vertically while retaining the tunnel geometry. The tunnel ceiling is slightly raised in the area of the portals and ends with a portal collar that is inclined backwards by 47.5 degrees and is approx. 2m high. A mechanical impact protection for the clearance height of 4.70m was arranged at each tunnel entrance. The impact protection is a beam-shaped concrete structure on the ceiling of the widened portal block. At the sides of the trough walls, embankments with attached noise barriers were formed, which also run around the portal. Ground-covering plantings are arranged on the interior embankment areas. The center wall of the tunnel cross-section is extended into the troughs over a length of 40 m at the north portal and over a length of 30 m at the south portal for ventilation separation.

2 Structure design

2.1 Tunnel

The foundation base of the tunnel lies in weathered to weathered mudstone, which is well suited for shallow foundations. The tunnel consists of 45 blocks with a block length of 10m each. The two-cell tunnel cross-section is a watertight reinforced concrete structure (WUB-KO) made of concrete C 30/37. Bituminous sealing was only arranged in the area of the underpassed roads. This has been covered with 10 cm of protective concrete. The outer walls have a thickness of 90 cm, the inner partition wall a thickness of 80 cm. With the useful widths mentioned above, the total width of the structure is 22.60m. The tunnel ceiling has a roof-shaped slope on the upper side, a thickness of 90 cm on the side and 1.20 m in the middle. The tunnel floor has a uniform minimum thickness of 1.20 m on lower roadway sides. The roadways are drained via slotted channels, which are connected approx. every 50 m to the longitudinal drainage pipes (DN 400) running in the structural concrete of the invert. There is a separate drainage pipe for each carriageway. The carriageway structure in the tunnel is 60 cm thick. At the low points, a DN 150 drainage system encased in filter concrete is provided in the subgrade with a connection to the inspection shafts of the longitudinal pipeline.

2.2 Trough structures

The trough structures adjoining the tunnel have 18 blocks in the north at a length of 178m and 14 blocks in the south at a length of138m. The block lengths are a maximum of 10m. They were also built as watertight reinforced concrete structures (concrete C 30/37). In the case of the trough structures, the foundation base is partly in the slope clay. To ensure uniform settlement behavior, the soil was replaced with 50 cm of ballast. The outer walls of the north trough have a thickness of 2.00 m at the bottom, which decreases to 1.50 m at the top. With the above-mentioned effective widths, the trough has a total construction width of 27.50 m. The trough bottom has the greatest thickness at the end of the portal, where it is 2.25 m thick. The thickness of the bottom slabs decreases towards the end of the trough as the depth of immersion in the groundwater decreases. The base slab has a uniform thickness across the entire width of the carriageway, and the adjustment to the transverse slope is achieved by means of a sloping concrete in which the longitudinal pipes are also located. The south trough has 2.00 m thick outer walls at the bottom and 1.50 m thick walls at the top; its total width is 27.89 m. The trough bottom is formed here without slump concrete as in the tunnel. The pavement in the trough sections is made of porous asphalt to improve noise protection, which is why specially adapted slotted channels were installed here for roadway drainage. In the entrance and exit areas, the structure was provided with a 3.00 m high, sound-absorbing lining over a length of 35.00 m in each case.

2.3 Tunnel equipment

The tunnel is equipped with all facilities for lighting, signaling, ventilation and smoke extraction as well as the necessary fire alarm and extinguishing systems in accordance with the guidelines for the equipment and operation of road tunnels (RABT). The traffic sign bridges at the tunnel ends were designed with inclined supports (fastened to the trough walls) in accordance with the design concept. To monitor and control these facilities, a single-story operations building was located on top of the tunnel in the area of blocks 2.21 and 2.22. The building, rectangular in plan, has dimensions of 15.50 m x 22.46 m, with a ridge height of 9.12 m, and was constructed of reinforced concrete with a wooden roof truss. The building stands on a layer of C 12/15 levelling concrete directly on the tunnel roof. The retention basin was located at the southern end of the tunnel, to which the wastewater and rainwater is fed via a DN 500 collection pipe. Via the combined retention and pollutant basin with the required separation facilities, the accumulating water is fed to the receiving water. The rectangular basin has ground plan dimensions of 13.80 m x 25.20 m and wall heights of approx. 4 m. It was built in reinforced concrete. It was built in reinforced concrete.

3 Construction

The tunnel and the two trough structures were constructed using the cut-and-cover method within a continuous excavation pit. The excavation was stabilized by means of a steel girder shoring system with shotcrete infill (reinforced concrete C 25/30). The shoring soldiers were tied back with strand anchors in two layers. After excavation in layers with corresponding production of the shotcrete infill, the floor slabs were produced in advance of the tunnel and trough walls. The excavation pit was dewatered by means of open dewatering. Drainage trenches with seepage pipes were constructed in front of each shoring wall and in the center of the tunnel in order to lower the groundwater level below the base of the excavation. These drainage facilities were grouted after completion of the structure to restore the natural groundwater level. The walls and slabs of the tunnel structure were constructed monolithically using a two-cell formwork carriage, while the trough walls were constructed using normal formwork. The walls of all parts of the structure were concreted directly against the shoring walls without any working space. A separating foil was used between the structural concrete and the shoring walls to reduce shrinkage. The strand anchors were not stress-relieved and remained in the ground together with the shoring soldiers and the shotcrete infill. Construction on the tunnel began in February 2012, and the structural work was completed in March 2014. The freeway section and the tunnel were opened to traffic on December 6, 2018. 

  • Country: Germany
  • Region: Nordrhein-Westfalen
  • Tunnel utilization: Traffic
  • Type of utilization: Road
  • Client: Bundesrepublik Deutschland, BMVI
  • Planning, Consulting Engineers: Landesbetrieb Straßenabu NRW; IMM, Bochum; Dr. Spang, Witten; WTM Engineers, München
  • Contractors: ARGE: A. Hörnig Bauges. mbH, Aschaffenburg; Stutz GmbH, Kirchheim
  • Main construction method: open cut
  • Type of excavation: cut-and-cover
  • Lining: in-situ concrete
  • No. of tubes: 1
  • Total length: 450 m, Trough North: 178 m, Trough South: 138 m
  • Clear width: 2 x 10,00 m
  • Construction costs: 25,2 Mio. EUR
  • Construction time: 3/2012 bis 10/2014
  • Traffic release: 6.12.2018