Bochum Light Rail, Contract Section E 1 /Rathaus-South Station

Contract section E 1 with the Rathaus-Süd Station was built in the centre of Bochum as part of the U 21 line of the rapid transit system, which is due to go into service in 2006. The contract consisted of 2 single-track route tunnels driven using the NATM by mining means with a total length of some 1,320 m, the Rathaus-Süd produced by the top cover method and a rail switching section. The Rathaus-Süd Station is devised as a generous, free-span hall without any sight-obscuring fixtures. The sophisticated design placed particular demands on planning and execution with the architects Pahl + Weber-Pahl already involved in the roughwork planning. The Station posseses a reinforced concrete folded slab roof, containing 13 ports so that daylight can enter right down to the platform. The folded slab roof and walls are made of exposed concrete. A further special Feature is Germany's sole underground bridge, on which the Line 306 travels through the "airspace" of the Rathaus-Süd Station. On account of the fact that normal services had to be kept running, including 3 tram lines, the folded slab roof was produced by the top cover method. After creating approx. 550 m of drilled piling to enclose the excavation pit, the ground was removed up to a working level required to produce the ceiling formwork. The construction of the 1.50 m thick folded slab roof took place in approx. 10 m long sections using approx. 88 t of structuraI steel reinforcement and 330 m² of B 35 WU concrete. After the ceiling of the roof was completed, work started on removing the earth and producing the floors and walls protected by the top cover. The station hall also served as the starting pit for the tunnel drives undertaken by mining means towards the Hauptbahnhof Station. Both single tubes were driven using tunnel excavators by the NATM. The length of advance amounted to 1 m and supporting was undertaken with shotcrete, 18 to 25 m thick, structural steel meshing and arches. The tunnels are mainly located in Labiatus marl (Upper Cretaceous) beneath the groundwater table. For the two-shell construction, the tunnels permanent lining was produced of 35 to 45 cm thick in situ concrete B 35 WU by means of a full-round formwork carriage so that it is waterproof. Over an approx. 160 m long section, the northern single-track tunnel penetrated a quaternary channel, which was filled with meltwater deposits and loess that tend to impede flow. Subsoil freezing was planned here. Protected by groundwater lowering from the surface with additional measures applied at the face, it was possible to drive this section safely even without freezing.

Country: Germany
Region: North Rhine Westphalia
Tunnel utilization: Traffic
Type of utilization: Underground, urban and rapid transit
Client: Bochum-Gelsenkirchener Stadtbahnverpachtungsgesellschaft des bürgerlichen Rechts (Stadtbahn GbR}
Consulting Engineer: Zerna, Köpper & Partner, Waning Consult, CDM Jessberger
Construction monitoring: Stadt Bochum Foundation Engineering Office
Contractor: Walter Bau-AG in association with Dywidag i. L.
Main construction method: Trenchless
Type of excavation: Excavator
Lining: Shotcrete
No. of tubes: 2
Tunnel total length: approx.860 m with 1,320 m of single-track tunnel. approx. 200 m station building produced by the top cover method
Cross-section: single-track tunnel: approx.36 m²/enlargement areas: approx. 90 m²
Contract Volume: approx. € 42 million
Construction start/end: July 1997 to May 2004
Opening: 2006