Prague subway - Refurbishment and maintenance of older lines

摘要

The first line of Prague's subway system, the Metro, was inaugurated 30 years ago. Today, the Prague Metro is operating a network of routes exceeding 50 km. The alignment of the lines lies largely beneath the ground water table, often within the Vltava River's flood-plain terrace. It passes under the river three times. This fact, combined with the fact that the initial tunnelling technique was based on the ring method adopted from the Moscow Metro construction, which was not capable of securing waterproof tunnels, causes the current huge demand for maintenance and refurbishment work. Without elastic filling, the joints between the reinforced concrete and cast iron segments are sources of significant leakage. The leaks had to be removed using polyurethane resins. Long-term sealing of the leaking joints, guaranteeing permanent elasticity and binding to substrate, has been achieved by a combination of injection materials and compounds. Our paper contains the experiences gained from the remedial operations, their results, and our recommendations.