Abstract

In-situ investigations were carried out for large power house caverns of the future pump storage power station Linth–Limmern, Canton Glarus, Switzerland. To investigate the bedrock at the cavern locations 10 horizontal to upward vertical inclined 50—130 m deep boreholes were drilled from an exploration tunnel and from two cross cuts. Many hydraulic and geotechnical borehole tests were performed. To estimate the hydraulic permeability in upwardly inclined boreholes two custom–made four–fold groundwater multi–level test systems were designed and built. These systems allow boreholes to be saturated so that hydraulic heads of the isolated borehole sections could be monitored and tested. The systems proved to be time–and cost–effective. The preferred in–situ testing provided site specific hydraulic and rock mechanical properties that were an essential element for design, tender and future construction of the caverns.

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