Tunnel Construction

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The excavation, as well as the stabilisation and support system works were carried out according to the New Austrian Tunnelling Method (NATM). The support system was done in two phases, one with shotcrete and expansion anchors and one with mortar anchors, welded wire meshes, and shotcrete.
The rock stabilisation functioned as a permanent supporting structure ("single-lining permanent support"), whereby higher standards were necessarily placed on the quality of the materials and on the construction. 13 measurement check points were installed for the technical measuring supervision of the support system (convergence measurements with five convergence bolts each, multiple extensometers, levellings, etc.). Work was done around the clock with three different shifts.

Stabilisation and Support System
"Single-lining permanent support": The rock stabilisation functions as a permanent supporting structure.





- 2 - 5 cm shotcrete (sealer)
- First layer: shotcrete 10-15 cm, welded wire meshes diameter 5/20/20, grouted anchors, N = 4,5-6,0-7,50m GEWI bar diameter 28 mm
- Second layer: shotcrete 10 cm HS Cement, welded wire meshes diameter 5/20/20

Structural Composition of Wall - Rock

Inlet gallery

The inlet gallery has a diameter of 3.9 m and a length of 930 m. Drilling was done with a TBM. At the same time, the inlet gallery served as a development drilling and reconnaissance gallery. In the area where the river Gader and the river Rienz merge, the single sewers are lead into the inlet galleries' intake structure. As a result of the sewer's depth level (5.0 m below the water level), substantial water containment works were necessary.

Cavern

a) Central Gallery 

Area of preliminary treatment	Area of technical chambers
Central Gallery consisting of: Coarse Screen Aerated grit chamber Bar-screen Dump Station Pre - thickeners Technical rooms	Technical Data Central Galley: Galley lenght: approx 325 m Full section 65 - 180 m² Excavation volume approx. 35.000 m³

 b) Side Galleries

Nitrification basins	Final clarifiers
Side Galleries consisting of: Preliminary clarifier Denitrification Nitrification Final clarifier	Technical Data Side Galleries: Galley lenght: approx . 325 m Full section 190 - 200 m² Excavation volume approx. 75.000 m³ je Stollen