Abstract
Constant head injection tests and radioactive tracer experiments at an experimental site in the Carnmenellis granite in Cornwall have revealed a fracture permeability in which water movement is confined to discrete fractures separated by rock of low permeability. Data on flow path frequency, orientation, and effective hydraulic aperture, required for network modelling, have been obtained for a 700-m borehole, with additional hydraulic data from three other boreholes. In addition to fractures of “average” hydraulic conductivity, a small number of major hydraulic features (“main drains”) with major implications for radionuclide migration have been identified. A mean hydraulic conductivity for the granite investigated of 1.57 x 10 −7 msec −1 has been obtained, 2.08 x 10 −8 msec −1 if the major hydraulic features (with hydraulic conductivities as high as 10 −5 msec −1) are excluded.
Published Version
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