The Panenská Tunnels

Owner:
The Roads and Motorways Directorate of the CR
Division Prague
Na Pankráci 56
Praha 4
 
Contractor:
Metrostav a.s.
Koželužská 5/2246
Praha 8
Division 5
Na Zatlance 1350/13
Praha 5
 
Designer:
Valbek v.o.s.
Vaňurova 505/17
Liberec 3
 
Table 1Basic parameters of the Panenská tunnel tubes
Basic data
Left (western) tube
Right (eastern) tube
Tube length
2 058 m
2 030 m
Mined section length
1 993.7 m
1 975.1 m
Length of cut-and-cover parts
64.3 m
54.9 m
Number of escape adits
9
9
Number of emergency lay-bys
3
3
Gradient
3.171 %
3.209 %
Crossfall
2.5 %
-4.0 %
3.5 %
2.5 %
-4.0 %
3.5 %
Theoretical excavated cross-section area   
75.55 m2 / 121.0 m2    
75.55 m2 / 121.0 m2
Net cross-section area
57.0 m2
57.0 m2
 
 

The two tubes of the Panenská motorway tunnel were parts of section G of construction lot 0807/II of the D8 motorway, which leads from Prague, past Lovosice and Ústí nad Labem up to the state border with the FRG. The D8 motorway links the German motorway A17 at this point, thus allowing motorway connection between Prague and Dresden. The motorway ascends through the Panenská tunnels to a plateau in the eastern part of the Erzgebirge Mountains (Krušné Hory).

As far as geology is concerned, the Panenská tunnels were driven through a faulted gneiss-crystalline system, which is interpenetrated with vein bodies of granitic porphyre. The construction of the Panenská tunnels itself was preceded by a detailed geological survey, including the driving of two exploration galleries, both from the northern and southern portals of the future tunnel.

The tunnels were driven on a down gradient, from the northern (Dresden) portal, using the NATM with a horizontal sequence (generally top heading, bench and invert). The excavation was supported according to the NATM support classes 4.2 to 2.1. Heavier support classes were specified for the sections which passed the vein bodies of granitic porphyry. The round lengths varied from 1.0 to 3.5m, depending on the excavation support class. The excavation support consisted, depending on the geology encountered, of the following primary support elements:
· welded mesh KARI 6/150 x 6/150 mm
· lattice girders
· C20/25 X0 shotcrete layers, 250 – 150mm thick, wet-sprayed
· 4.0m or 6.0m long rock bolts, expanded by pressurised water, in the top heading; 4.0m or 6.0m long SN-anchors with the capacity of 12 ton; IBO anchors at corresponding lengths in the cases of instability of boreholes
· pre-bored steel dowels 25mm in diameter and 4.0m long, installed in the cases of instable top heading
The drill-and-blast operations were carried out using high-performance, modern wheeled equipment.

The final lining of the tunnel was a 400mm thick cast-in-situ reinforced concrete structure (concrete grade C25/30 XF4), which was divided into footings and a vault. An invert was not required with respect to the encountered geological conditions and favourable development of convergences.
The individual blocks were 12m long in the vault, which means that about 150m3 of concrete were necessary for the casting of one block. The total volume of concrete placed in the final lining amounted to 50,000m3.

Part of the final lining was a 2.5mm thick intermediate PE membrane, forming, together with longitudinal drains, a so-called open waterproofing system, which diverts seepage ground water.

The 22.930km long stretch of the D8 motorway leading from the border with Germany to Trmice, comprising the Panenská tunnels and adjacent motorway sections, was opened to traffic on 21st December 2006. As a part of the opening events on both Czech and German sides, representatives of both neighbouring states ceremonially cut the tape.