Employer
Nant de Drance SA, CH-1925 Finhaut
Designing Engineer and Site Supervision
AF-Consult Switzerland Ltd, CH-5405 Baden-Dättwil
Time of Completion
08.2008 – 12.2018
Contract Sum
CHF 745 Mio.
Execution of the Work
GMI Groupement Marti Implenia
Consortium Partners
Marti Tunnel AG, CH-3302 Moosseedorf
Implenia Bau AG, CH-5000 Aarau
Lead Company and Technical Lead
Marti Tunnel AG, CH-3302 Moosseedorf
Commercial Lead
Implenia Bau AG, CH-5000 Aarau
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Project description
The Nant de Drance project consists of the conversion
of diverse existing power stations in an underground
pump storage plant in order to achieve an installed
power of 900 MW (6 units of 150 MW each) and increase the water retention capacity of the upper reservoir of Vieux Emosson.
The main project construction elements are:
- 5’600 m long access tunnel
- 2 x 1‘500 m surge tunnels
- 2 x 430 m vertical pressure shafts
- Turbines and transformers caverns
- 4’500 m of access and services galleries
- Intake and discharge structures Vieux Emosson with Fangedamm
- 20 m dam elevation of Vieux Emosson
Work description
- Access tunnel excavation with a hard rock TBM: L= 5’600 m, ø=9.4 m
Performance of injections and consolidating grouting
to prevent dam settlements and mountain hydraulic
discharge caused by the “La Veudale” fault crossing.- 7’500 m of excavation of surge tunnels as well as an
access and service gallery complex by means of drill
and blast in a section range of 46 to 65 m².- Two, 8 m in diameter, pressure shaft excavation with
raise boring and D&B sinking- Caverns excavation using conventional methods
Turbines cavern: L= 190 m, B= 32 m, H= 52 m
Transformers cavern: L= 127 m, B= 23 m, H= 25 m- Powerhouse concrete lining, construction and architectural works
- Surge tunnels and pressure shafts lining
- Construction of intake and discharge structures
- Dam elevation Vieux Emosson 20 m height increase, storage capacity extension to 24 Mio. m³ and a longitudinal development of 200 m
Concrete volume: 62’000 m³- Aggregates production plant for processing of
600’000 t of concrete aggregates- Installation of two batching plants: underground and
at the portal. Concrete production of over 365’000 m³- Material management: transport of tunnel masses
and processing of 1.2 Mio. m³- Damlike landfillings and disposal works
- Implementation of a conveying system (engineering,
design, manufacturing) of: 5’540 m long conveyor
belt for the transport of the TBM muck
General Conditions
- Alpine work conditions at altitudes of 1’000 to 2’300 m
- Extreme winter weather conditions
Contact
Marti Tunnel AG
Seedorffeldstrasse 21
CH-3302 Moosseedorf
Tel. +41 31 388 75 10
tunnel@martiag.ch
