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HIGH OVERBURDEN TUNNELS

Gerede tunnel bifurcation chamber

ANKARA WATER SUPPLY PROJECT
(TURKEY)

The Ankara Water Supply Project aimed at divert the Gerede river through the construction of a headrace tunnel that will transfer the water to the area of the Çamlıdere Dam. The planned tunnel is a free-flow conduit, 31.6 km long with an inner diameter of 4.5 m which gives it a transport capacity of 40m3/s. Due to geological conditions with presence of medium to slightly weathered volcanic rocks (basalt, andesite and volcanic breccia) and a ground overburden up to 600 m, two different types of lining are foreseen. In addition, a high inner water pressure is expected, so the waterproofing design was critical since the tunnel has to be watertight up to 10 bar and at the same time guarantee water ingress into the tunnel at that pressure. The lining has been designed with a pressure relief valve located in the pea-gravel injection hole.

Tunnelconsult designed the precast segments for both ring lining types, reviewing the segments formwork, waterproofing characteristics and providing technical support in gasket design & selection and pressure release valve specifications.

BBT TBM "Glon" front view of the cutter-head

BRENNER BASIS TUNNEL
(AUSTRIA-ITALY)

With a 63 km long, the Brenner Basis Tunnel (BBT) is the most important infrastructure project of the Scandinavian-Mediterranean Corridor which will connect Finland and Sweden in the northern Europe with Italian ports in the south, representing the overcoming of the Alps barrier. Running under 1700 m of complex rock mass massifs, its construction includes the excavation of two 9.04 m inner diameter single-track tunnels, separated about 70m and connected between them via transversal galleries. On the axis of railway tunnels 11m underneath, an Exploratory Tunnel will be bored to be used firstly as final geological investigation and finally as emergency access. The BBT DS TBMs use several investigation techniques to provide information on ground and rock conditions several meters onwards, helping engineers to adapt TBM advance for better and more efficient performance, given the foreseen geomechanical hazards such as squeezing, face instability, precious water resources to be preserved.

Tunnelconsult provides its expertise for TBM selection criteria, designing TBMs launching frames and precast segmental lining (geometry, materials and manufacturing processes), as well as defining the methodologies for TBM advance, interpretation of data from boreholes in advance (150m every 100m) and geophysical test, drainage ahead of excavation and lining monitoring. Finally, the identification of the stretches where consolidation is needed are also identified and the required intervention are designed based on the actual condition. 

TBM excavation front detail

SAINT-MARTIN LA-PORTE 3 TRANSALPINE LYON-TORINO RAILWAY LINE
(FRANCE)

The Transalpine Lyon-Torino Railway Line Project is a major infrastructure leading to connect France and Italy under the Alps in order to improve the railway transport in this area. In Saint-Martin La Porte (France) it was projected an 8.8 km long exploratory tunnel to connect with the southern stretch of the main basis tunnel (57 km long). The exploratory tunnel has been bored by a Single Shield Hard-Rock TBM of 10.94 m of excavation diameter, under 1080 m of ground overburden.

Tunnelconsult provided technical consultancy to the Project Manager in the excavation of the exploratory tunnel SMP3 by TBM, with the definition of TBM technical specifications, review of the segmental lining design and improvement measures and methodology of anular vacuum filling.

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