The tunnel is taken through the soil environment of the slate and siliceous sandstone of Silurian and Ordovian period. Its larger part in the length of 1283 m will be driven, only part near Lochkov will be cut-and-cover. For the driven part the new Austrian tunneling method is being used, which takes advantage of the load-bearing properties of the rock massive to the maximum. The method allows optimization of the driving process and security of the stope and thus optimizes the construction costs. The driving is done by mechanical machine disintegration in combination with blasting. The behaviour of the massif is continuously monitored and measured in the place of the tunnel as well as on the surface. On the basis of thus obtained data the number and the placement of the drill holes for the explosives is adjusted.
The part of the tunnels in insufficient depth beneath the terrain will be concreted in the open construction pit and after the completion covered up by the soil. Because it is necessary during the construction to transport large quantities of the construction material, it was important to establish in the vicinity of the site a temporary mobile concrete mixing plant for the permanent walling of the tunnels. It will simplify otherwise complicated transport of the required quantity of the concrete.
In the cut-and-cover sections of the tunnel between Lochkov and Radotín the earth works are currently finished and the works for the preparation of the monolith structures are continuing. In the driven part circa 320 meters of the two-lane tunnel and circa 140 meters of the three-lane tunnel were completed by the end of March. As well as the tunnel, HOCHTIEF CZ takes also part in the construction of the bridge over the Lochkov valley, where the construction works are yet to start – i.e. earth works and founding of the substructure of the bridge.
On the site there are around one hundred builders working constantly and a large quantity of specialized building technology. The working activities are difficult in coordination of the individual stages and so it is very important that the working team comprising of the German specialists of HOCHTIEF Construction AG and the Czech professionals of HOCHTIEF CZ was in harmony.
The construction of the tunnels between Lochkov and Radotín commenced in June last year and its completion is planned for the end of year 2008. The installation of the technology will follow and should take till October 2009.
Other technical data about the construction of the tunnels:
Driven out soil 310 000 m3
Construction concrete 90 000 m3
Concrete reinforcement 9 000 t
Amount of explosives 200 t
Construction pit of the cut-and-cover tunnels 230 000 m3
Backfill of the cut-and-cover tunnels 130 000 m3
Area of the stope of the two-lane tube 100 m2
Area of the stope of the three-lane tube 136 m2