characteristic

About one third of the length of operating lines of the Prague Metro found in the central area of Prague were inundated during the flood in August 2002. The construction of a new flood-protection system commenced immediately, when the damage caused by the flood had been repaired and the metro lines operation had resumed. Analyses and the assessment of the flood impacts showed that the flood wave threatens most of all cut-and-cover structures of the metro lines which are founded near to the surface, namely by increased external hydrostatic pressure and/or the hydrodynamic effects of this pressure. Mined metro sections are virtually unthreatened in these cases. Protection of the cut-and-cover structures is provided by several basic types of traditional construction measures. The structural parts found in the flooded zone are reinforced or thickened, permanently anchored, braced or supercharged. Structures which are selected with respect to their design and local hydrogeological conditions are provided with elements relieving the hydrostatic pressure on the outer surface of stations and concourses.