THE CONSTRUCTION LOT IN FIGURES
3.026 km of main tunnel excavated southwards
of exploratory tunnel excavated southwards
Connecting tunnels and cross passages
Conveyor belt to the H41 Sill Gorge-Pfons construction lot
Contractor: Swietelsky Tunnelbau GmbH & Co KG
Contract value: 120 million EUR
COMPLETED
All tunnelling work on this construction lot was completed in November 2023.
EXCAVATION DATA
- Excavation 3,026 m
- Length 3,026 m
- Cross-section 60-80 m²
- Excavation 863 m
- Length 863 m
- Cross-section 60 m²
- Excavation 970 m
- Length 970 m
- Cross-section 25-30 m²
COMPLETED WORK
- Construction of an auxiliary drivage from the exploratory tunnel to the main tunnel tubes in the Hochstegen zone, and tunnelling work in these areas from the auxiliary drivage.
- Excavation through the northern transition to the Hochstegen marble formation in the exploratory tunnel and in the main tunnels, and injection measures in the area of the exploratory tunnel in the Hochstegen marble.
- Excavation of the crossover point and installation of an approx. 9 km long conveyor belt to the H41 Sill Gorge- Pfons construction lot.
EXCAVATION METHODS
DRILL & BLAST:
All structures in this construction lot, with a total length of 4.8 km, were excavated by blasting: the exploratory tunnel and the main east and west tunnels southwards, as well as the connecting tunnel (crossover point) and the cross passages. Excavation in this area was carried out under the protection of advanced sealing and stabilization injections.
SPECIAL FEATURES OF THE CONSTRUCTION LOT
The focus of this construction lot was the excavation of the exploratory tunnel southwards through the so-called Hochstegen zone. This is a geological fault zone: the Hochstegen marble marks the boundary between the Triassic and Jurassic geological eras.
The fault zone extends over approximately 500 metres and features carbonatic and water-bearing rock layers. This made the tunnel excavation in this stretch particularly challenging. As the water pressure was over 50 bar, advanced sealing and stabilization injections were necessary to consolidate the rock. These injections were intended to prevent both water inflows and a lowering of the water levels in the protected areas Hinteres Venntal and Hinteres Valsertal-Natura 2000 and to significantly reduce the water inflow quantities.