Abstract

Part of the on-going research effort of the international Stripa Project, based at the Stripa Mine in Sweden, involves a site characterization and validation programme (SCV). This comprises investigation of a block of fractured crystalline rock some 250 × 250 × 100 m in extent penetrated by 12 angled boreholes drilled from tunnels in the mine. The SCV is intended to represent the type of investigation which might occur at a repository site during construction to identify significant flow pathways through the rock mass as well as volumes of ‘good rock’. A staged approach of investigation has been employed in which periods of measurement have alternated with periods of conceptual and mathematical modelling. Predictions have been checked by additional measurements. A variety of single borehole geophysical (radar and seismic), geological mapping, geochemical and hydrogeological (a novel focused packer system) techniques have been employed in the early stages to construct a conceptual model of fracture flow within the rock mass. Mathematical models, based on a fracture-network approach, have been constructed from these data and used to predict fluid flux into the purpose-built boreholes and tunnels. The measured flows, together with transmissivity distribution information derived from inter-borehole hydraulic interference testing, were compared with the predictions and showed good agreement, building confidence in this approach. New models of flux and transport have been developed which incorporate the additional measurements.

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