Light Rail Bensberg Central

Since it was opened in 1906, Line 1 of the urban railway has ended on the outskirts of Bensberg. The town centre could only be reached by switching to buses, a not particularly convenient procedure. The new section of line means that the centre of Bensberg is not joined up directly with the Cologne urban railway network. The altogether 487 m long construction lot is, by and large, divided into 3 different sections. The first is an approx. 100 m long 2-track line section, which was created by cut-and-cover. This is followed by an approx. 240 m long 2- track section driven by mining means. The third section is an approx. 120 m long station with a central platform and underground parking facility, which was also built by cut-and-cover. The tunnel driven by mining means was shotcreted and has an overburden of between 2.5 and 4.5 m. The excavated cross-section extends from 66 m² at the end of the cut-and-cover section to 130 m² at the start of the station. A single-horseshoe wall bench heading was chosen in order to ensure that the maximum excavated cross-section could be restricted to 45 m² ln the enlargement area, a third part-excavation was essential on account of the size of the excavated cross-section. However, this could first be accomplished for static reasons once the inner shell had been installed in the first 2 part-excavations. The shotcrete is some 25 or 20 cm thick in the wall segment. Roughly in the centre of the mined section, business premises had partly to be undercut with the gap to the tunnel roof only amounting to 1 m. ln order to avoid unacceptable Settlements affecting the surrounding buildings, 2 advance pipe screens each with 29 steel pipes (14 cm diameter, wall thickness t = 1 cm, length 12.5 m) were installed from the heading. Following grouting and filling of the pipes, the heading could be resumed protected by the pipe screen. The final lining was made of watertight WU concrete 35, which is separated from the outer shell by means of a nonwoven fabric. The 25 individual blocks of the mined tunnel are split up into 3 sections on account of the cross-section enlargement. The first 10 blocks could be executed in the classical base-vault manner. The cross-sections of the 6 blocks that follow had to be continuously enlarged. In this connection, a hydraulic formwork car with a straddling device for the sheathing was necessary. The third section (9 blocks) with the largest cross-section had to be completed in 2 parts. ln this connection, after finishing the first part-excavation, half of the inner shell with central wall (6 blocks) and provisional central steel supports (3 blocks) had to be created. The inner shell was then completed by undertaking the second part-heading.

• Country: Germany
• Region: Nordrhein-Westfalen
• Tunnel utilization: Traffic
• Type of utilization: Underground, urban and rapid transit
• Client: Kölner Verkehrsbetriebe AG, Stadt Bergisch Gladbach, Stadtbahngesellschaft Rhein–Sieg
• Consulting Engineer: Prof. Dr.-Ing. B. Maidl Ingenieurgesellschaft mbH, Ed. Züblin AG
• Contractor: Ed. Züblin AG
• Main construction method: Open/Trenchless
• Type of excavation: Cut-and-cover/Excavator
• Lining: Concrete formwork
• No. of tubes: 2
• Tunnel total length: 487 m (including 1 Station)
• Cross-section: 66 to 130 m² (mining means)
• Contract Volume: 34 mill. DM
• Construction start/end: 1997 to 1999
• Opening: 1999