Tunnel water

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As tunnel water is underground water refers to the columns and from water-bearing strata in lying above the groundwater level tunneling and tunnel penetrates.

Tunnel construction phase

While the tunnel is being built , the construction teams repeatedly come across mountain water in the rugged rock, which penetrates the freshly excavated cavities. Quantities of up to 400 liters / s can occur. Structural measures must be taken to prevent this water from penetrating into the later tunnel vault. It is later drained through the vault drainage. Mountain water often contains sulphate or chloride , and in such cases one speaks of aggressive mountain water .

For cooling and cleaning, fresh water is supplied during the construction phase, which has to be drained out of the tunnel and which often has too high nitrite concentrations due to explosive residues . Other pollutants such as AOX , mineral oil hydrocarbons (MKW) , oil, suspended matter and high pH values can occur. Just like aggressive mountain water, this waste water must be treated and cooled in water treatment plants outside the tunnel.

Tunnel operating phase

During the operating phase, tunnel water is drained out of the tunnel in sewer lines below the carriageway or the route. A protective film around the concrete casing is intended to protect the tunnel tubes from ingress of water and to divert the mountain water on the outside of the tube. Due to the thermal conditions, especially in the case of high overburden , these fissure waters can reach temperatures of up to 25  ° C , and temperatures of over 25 ° C are expected for the new base tunnels of the Swiss NEAT .

Geothermal use

In Switzerland, the potential of these freely available heat sources was recognized as early as the 1970s , not least as a result of the energy crisis of 1973 . The Airolo motorway depot , which opened in connection with the Gotthard road tunnel in 1979 , is heated and cooled using the thermal use of the tunnel water emerging from the south portal. This unusual hot water source, which gushes at 400 m³ / hour and temperatures of 16-18 ° C initially, would have the potential to generate a heat output of 6 megawatts with the simultaneous use of decentralized heat pumps , which is sufficient for the heat supply of a large part of the village of Airolo would. The heat pump system in Airolo is the first of its kind. The system has proven itself to this day.

A total of five systems in Switzerland use warm tunnel water
Tunnel system Amount of water Water temperature Heating energy Geothermal. energy place use
Gotthard road tunnel 7200 l / min 15 ° C 6.99 GWh 4.99 GWh Airolo TI Airolo motorway depot (see above)
Furka Base Tunnel 5400 l / min 16 ° C 5.0 0GWh 3.57 GWh Oberwald VS 177 apartments, 1 multi-purpose hall
Hauenstein 2500 l / min 19 ° C 0.67 GWh 0.48 GWh Trimbach SO 150 apartments
Rickentunnel 1200 l / min 12 ° C 0.25 GWh 0.18 GWh Kaltbrunn SG several public buildings
Mappo Morettina Tunnel 0250 l / min 11 ° C 0.58 GWh 0.42 GWh Minusio / Tenero TI Mappo Sports and Recreation Center
Extreme values
Tunnel system Amount of water Water temperature Potential when cooling to 10 ° C use
Grenchenberg tunnel 24,000 l / min 13 , 0° C 5 , 0MW z. Z. unused
Rawyl exploratory tunnel 1,200 l / min 24.3 ° C 1.2 MW z. Z. unused
NEAT base tunnel
Tunnel system place Amount of water Water temperature Energy potential use
Gotthard Base Tunnel Erstfeld portal 060-555 l / min 30-34 ° C 33 MW District heating use planned
Lötschberg base tunnel Frutigen portal 150-200 l / min 18-22 ° C 15 MW Local heating network Tropenhaus Frutigen [1]

See also

Web links