Intersection Stadtbahn/Tunnel B 61n

Two tunnel tubes (tracks 31 and 32) for the urban railway completed in carcass state were located beneath the road tunnel. Owing to a change in the network, a turn-off had to be created at this point (tracks 61 and 62). As a result, the construction of a turn-off building was necessary in conjunction with the intersection building. In order to construct the intersection building, urban railway track 62 was driven with an enlarged cross-section beyond the intersection zone. From this part of the tunnel, crosscuts with an advance crown were driven, which achieved considerable dimensions - 12.00 m high and approx. 6.00 m wide. During the driving of the crosscuts, the existing tunnel tubes for the urban railway had first of all to be partly broken off. In the crosscuts, wall sections were created with the foundations, designed to divert the vertical and horizontal forces from the road tunnel and the new urban railway tubes into the subsurface. In this connection, construction work turned out to be very tricky. Thankfully, the entire intersection building is located in healthy, hard clay stone, which is flatly bedded, possesses few fissures and cleavages and carries only small amounts of groundwater. The approx. 215 m² large excavated cross-section was driven in 5 part-cross-sections with excavated sections of 33 m² (lateral tunnel) to 47 m² (central tunnel). The excavated cross-section was secured by means of steel arches with two layers of reinforcement. The permanent inner vault was made of watertight reinforced concrete.

• Country: Germany
• Region: Nordrhein-Westfalen
• Tunnel utilization: Traffic
• Type of utilization: Light rail
• Client: Stadt Bielefeld
• Main construction method: Trenchless
• Type of excavation: excavator
• No. of tubes: 1
• Tunnel total length: 30 m
• Cross-section: up to 215 m²
• Construction start/end: September 1986-March 1989