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Hydraulic conductivity distribution in crystalline rocks, derived from inflows to tunnels and galleries in the Central Alps, Switzerland = Distribution de la conductivité hydraulique dans des roches cristallines, déduite des flux entrants dans des tunnels et galeries des Alpes centrales, Suisse

Masset, Olivier ; Loew, Simon

In: Hydrogeology Journal, 2010, vol. 18, no. 4, p. 863-891

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    Titre
    • Hydraulic conductivity distribution in crystalline rocks, derived from inflows to tunnels and galleries in the Central Alps, Switzerland
    Titre traduit ()
    • Distribution de la conductivité hydraulique dans des roches cristallines, déduite des flux entrants dans des tunnels et galeries des Alpes centrales, Suisse
    Auteur
    • Masset, Olivier. Geologisches Institut, NO G 69.1, Sonneggstrasse 5, 8092, Zurich, Switzerland
    • Loew, Simon. Geologisches Institut, NO G 69.1, Sonneggstrasse 5, 8092, Zurich, Switzerland
    Type de document
    • Postprint
    Identifiant OAI-PMH
    • oai:doc.rero.ch:321258
    Summary
    Inflow data from 23 tunnels and galleries, 136km in length and located in the Aar and Gotthard massifs of the Swiss Alps, have been analyzed with the objective (1) to understand the 3-dimensional spatial distribution of groundwater flow in crystalline basement rocks, (2) to assess the dependency of tunnel inflow rate on depth, tectonic overprint, and lithology, and (3) to derive the distribution of fracture transmissivity and effective hydraulic conductivity at the 100-m scale. Brittle tectonic overprint is shown to be the principal parameter regulating inflow rate and dominates over depth and lithology. The highest early time inflow rate is 1,300l/s and has been reported from a shallow hydropower gallery intersecting a 200-m wide cataclastic fault zone. The derived lognormal transmissivity distribution is based on 1,361 tunnel intervals with a length of 100m. Such interval transmissivities range between 10−9 and 10−1m2/s within the first 200-400m of depth and between 10−9 and 10−4m2/s in the depth interval of 400-1,500m below ground surface. Outside brittle fault zones, a trend of decreasing transmissivity/hydraulic conductivity with increasing depth is observed for some schistous and gneissic geological units, whereas no trend is identified for the granitic units