Verification of large-scale permeability tests in hard rocks

In Norway, ten so-called "air cushion surge chambers" have been constructed as integrated parts of the hydraulic systems for underground hydro power plants. The safe and economic planning and operation of these air cushions requires a good understanding of the hydrogeological conditions in the rock mass around the air cushion cavern. A proper design should be based on reliable parameters for the permeability of the rock mass. This paper will describe long series of permeability tests and how the results from these tests were treated. It will also discuss the procedure for the selection of representative permeability coefficients for modelling, and the quality of the selected coefficients will be verified by control measurements in the field. Firstly a description of the air cushion surge chamber is given.