Metro Shall Have A Single-Nave Station
Released: 6. 12. 2002
On Thursday, December 5, the Transportation Utility of the City of Prague and Metrostav, Joint-Stock Company, presented to the expert community a unique space of the future station “Kobylisy” on the IV.C metro line. This driven station with an island platform, which is in an approximate depth of 31 meters under the ground, is the first one of this kind in the world, since it is designed as a “single-nave” – it shall be built in a large cross-section tunnel with a profile of 220 square meters and a length of 148 meters. No columns, no piers shall be around the central platform so that a spacious and well-lit single space shall be created. This unique technical work was presented to expert public in an unconventional manner: the giant tunnel resembling an underground cathedral hosted a dance show of Kristýna Lhotáková and Ladislav Soukup. Their high-spirited, courageous performance multiplied the impression raised by this artificially created underground hall.
Within the project of the “Kobylisy” single-nave station, Metrostav fully used their abundant experience and practice with construction of large cross-section tunnels in Prague (especially tunnels of “Mrázovka”). To build the “Kobylisy” station, the cross-section was structured vertically; firstly, two side partial tunnels were driven, ceilings of which were shaped as a lancet arch. Then, the middle part between these two caves was mined out to form the entire cross-section. The implementation was extremely demanding, because geological conditions in the given locality are markedly different from conditions in other parts of the city, where the Prague Metro was built. Where the tunnel was driven in quartzite layers, it was needed to use explosives; however in a very cautious and sensitive manner, since a real danger impended that the otherwise steady-state groundwater table could raise. Just a permanent groundwater affluent of 10 liters per second made all and any driving works being carried out in the Kobylisy station more difficult and made heavy demands on proper management of the project. The fact that the tunnel was driven in a very densely populated area with numerous crucial underground services had taxed project managers in terms of coordination with manifold PLCs.
Particulars of Driven Single-Nave “Kobylisy” Station
● station total length 148 m
● total area of rough stope 220 m2
● volume of mined out natural ground 32 560 m2
● thickness of twin-shell lining
with intermediate insulation 1 m – 40 cm primary
– 60 cm secondary
IV.C1 Metro Line
The IV.C1 metro line being under construction, which shall be put into operation in mid-2004, shall extend the existing C–line by 3,981 m and it shall connect the North Town with the city center. This line, price of which shall be CZK 4.7 milliard (US: billion), begins in the existing station – “Nádraží Holešovice” (Railway Station Holešovice), then it goes under the Vltava River, and on the other bank it steeply rises towards Kobylisy and Ďáblice. In constructional terms, this section includes certain unique places.
To cross the Vltava River, experts of Metrostav, a.s., have developed a brand-new technology of launched tunnels. This launching technology was used for tunnels of such size and under such conditions for the very first time and rightly it commanded attention of world expert circles (Prize of fib 2002 congress, nomination for the prize of Eurowards 2002, and Prize of Engineering Academy of the Czech Republic).
The IV.C line also includes three sections of double-track tunnels brining better comfort for passengers. With regard to the fact that metro trains shall go in both direction in a single tunnel tube, no air draught shall be generated in stations, which should otherwise occur in cases, where trains go through tight single-track tunnels (the difference between the structural gauge and loading gauge is small).
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spokesman Metrostav a.s.
Tel.: +420-266 709 294