Porosity and Focused Dissolution of Granitic Rocks in Two Study Areas in Southern Finland: Aspects of Methodology

摘要

The document is principally a description of methods for classifying the effective porosity of rock and modeling water-rock interaction in pore spaces in rock. Two Proterozoic granitic intrusions in southern Finland, a synkinematic tonalite and a postkinematic rapakivi granite, were examined. The effective porosity of granites is due to fractures, microcracks and tube-like diffusion pathways. Fracture zones and fractures are classified according to fracture spacing, frequencies, and the nature of infillings. Microfractures are classified according to their locations and extension within mineral grains. A rectangular geometry for rock fractions, such as rectangular 'fracture fractals', was identified at both mesoscopic and microscopic scales. Natural groundwater equilibrium and mineral saturation states of the intrusions were calculated with an EQ3NR program. A reaction surface area of rock can be considered equal to a surface of effective rock pore space. The study comprises part of the nuclear waste research program of the Geotechnical Laboratory (GEO) of the Technical Research Centre of Finland (VTT). The two areas studied here are the nuclear power plant sites of Imatran Voima Oy and Teollisuuden Voima Oy. Aspects of spent fuel disposal are emphasized but the results can also be applied to rock mechanics and building stone investigations.