The article describes geologic conditions, investigations performed and design criteria for unlined high pressure tunnels and air cushion chambers. The economic advantages of unlined pressure tunnels for the upper portion of the head instead of steel lined shafts all the way to the top are discussed. Further, the paper discusses the decision of adopting the air cushion chamber solution for the Lang-Sima system. Problems related to establishing access to unlined high pressure tunnels are also described.
Der Artikel beschreibt geologische Verhaltnisse, durchgefuehrte Erkundungen und massgebende Kriterien fuer die Ausfuehrung von nicht ausgekleideten Hochdruckstollen und Luftkissenkavernen im Fels. Wirtschaftliche Vorteile bei ungekleideten Druckstollen statt gepanzertes Ausbau einer oberen Stufe des Gefalles wird behandelt. Weiterhin wird der Beschluss beim Kraftwerk Lang-Sima eine Luftkissenkaverne zu verwenden diskutiert. Probleme, die mit der Etablierung von Zutritt zu ungekleideten Hochdruckstollen verbunden sind, werden auch diskutiert.
L''article decrit les conditions geologiques, les reconnaissances de terrain et les criteres de design pour tunnels de haute pression non-revetus et pour chambres a coussin d''air. Les avantages economiques des tunnels non-revetus pour la portion superieure de la tete d''eau relativement aux tunnels revetus d''acier tout Ie long de la perte de charge sont discutes. L''article decrit en plus les raisons du choix de chambres a coussin d''air pour Ie complexe Lang-Sima. Les problemes relatifs a l''acces aux tunnels non-revetus sous haute pression sont aussi discutes.
The Sima project started in 1920 when Osa Fossekompani A/S began building a power station in Osa, in the municipality of Ulvik, Hardanger. Work was however discontinued then. During World War II, the Germans, planning an aluminium plant in Osa, resumed the work. After a short time the project stopped once more.
In 1962, the State Power System made a fresh start at the project and extended considerably the area covered. In 1973, a reduced plan for development of Eidfjord North was adopted by the Norwegian Parliament Stortinget. The plant was named the Sima Power Plant.
(Figure in full paper)
The power station''s four generating sets have a total output of 1120 MW and the annual output of power is about 2800 GWh (2800 million kWh). The entire power works cost 2000 million kroner, exclusive of interest during the construction period.
The Sima power station uses water from two geographically separate areas and properly speaking consists of two stations, Lang-Sima and Sy-Sima, installed in one generating hall.
Below 1000 meters, the Sima region consists of Precambrian rocks, mostly gneiss and granite, covered locally by phyllites of Cambro-Silurian age.
Loose material from the late Quarternary age is found on hillsides and valley bottoms. Exposed bedrock occurs frequently in the mountainous area.
The upper parts of the Sima River system, inclusive of AustdØla, are diverted to Langavatn. Langavatn, one of the intake basins, gave rise to the abbreviated name Lang-Sima. Langavatn is dammed up by rockfill dams. The reservoir has 48 metres of working storage and top water level at 1158 metres above sea level. NorddØla is diverted to Rundavatn, the other intake basin. Rundavatn is dammed up to 1040 metres above sea level by a rockfill dam.
The two Lang-Sima generating sets can run alternately on water from Langavatn or Rundavatn.
From the intakes, the water is carried to the valve chamber at Kjelsen through one common, unlined tunnel, 8 kilometres long with a cross-sectional area of 30 square metres. The Kjelsen area is 600 metres above sea level. The maximum water pressure in the unlined section of the supply tunnel is 525 m.
