The City Circle Road in Prague – The Mrázovka Tunnel

Prague, Czech Republic
Tunnel complex is located inside the city of Prague, on the western part of the City Circle Road (CCR). The initial design drafts for this section of the CCR project from the 1990s gradually switched from subsurface roads to tunnel structures.
The total length of the tunnel amounts to 1300m for the western tube and 1254m for the eastern tube. The major part of the tunnel was built by mining methods (the total mined tunnel length is 2481m); the northern cut-and-cover section added about 35m and the southern about 300m to its length.
The technical services facilities comprised the main underground ventilation plant and transformer station, which were located in a cavern excavated under Paví Hill, and a ventilation tunnel and shaft connecting the cavern with an at-grade exhaust structure. Other technical services were installed in the construction trenches at all portals of the mined tunnels. Both main tunnel tubes are interconnected by a total of six cross passages; there is one lay-by in the western tunnel tube for the operation of the underground technical service facilities.
Two parallel three-lane mined tunnel tubes ( driven by NRTM) run from the northern portal. Both three-lane tubes split in bifurcation chambers into double-lane mined tunnels, which continue along the alignment of the City Circle Road, and single-lane branches, which are connected to Radlická Street. The cut-and-cover tunnels are connected to the mined double-lane tunnels at the portals in Radlická Street. The design speed is set at 70km/h. The maximum longitudinal gradient on the main route amounts to 4.5 percent; on the single-lane branch up to 6 percent. The smallest radius of a horizontal curve is 195m for the double-lane tunnel, 400m for the three-lane tunnel, and 100m for the single-lane branch. The traffic lanes are 3.5m wide; the clearance profile is 4.8m high. Three-lane tunnel has a cross section
160 m3, bifurcation part of tunnel split has a cross section 340 m2.
Additional pictures

- Underground Transport
- Road tunnels
7.032 billion.CZK / 235 mil. EUR

- Architectural quality of urban environment has to be improved
- Service quality of the urban environment has to be improved
- Safety and security in urban environment has to be improved
- Additional traffic capacities are needed for public transport
- Additional traffic capacities are needed for individual and freight transport, Relief from traffic congestion is needed
- Time savings in transport are necessary
- Noise levels are not acceptable
- Pollution (esp. air pollution) is not acceptable
The basic road system of capital Prague is formed by three rings which are cut across by radial roads. Build-up of the middle ring started by construction of bridge across river Vltava, and by so called Strahovsky tunnel. Then it was necessary to find suitable technical solution of transport interconnection these two constructions. Initial idea which seemed to be the best solution was surface road arrangement. Expected density of transport was 50.000 cars/day. Comprehensive analyses of elaborated options showed disadvantages of such surface solution – splitting of adjacent urban area by heavy transport and traffic congestion forecasted unacceptable impact to environment – noise and air pollution. Finally underground variant was accepted by City Authority. Tunnel interconnection enables smooth traffic flow that leads to reducing of emissions, noise and travel time. Operation in this tunnel complex is supervised from two dispatching centers consecutively. Installed detection system
enables determine place of fire with accuracy of 1.5 m, at entrance tunnel portal red light indicates no drive in and on the opposite portals green light enables quick evacuation of cars inside tunnels. Four transversal corridors for passengers and two galleries for fire brigade cars make possible evacuation and fire liquidation in very short time.