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An analysis of a series of chalk samples from the Lublin coal basin reveals that its matrix is a very porous but only slightly permeable porous medium; its water reserves are hardly susceptible to gravity drainage. The interconnected porosity of the chalk matrix diminishes with depth, probably because of the increase in lithostatic pressure.Les propriétés hydrogéologiques de la matrice de la craie dans le bassin houiller de Lublin (sud est de la Pologne) Résumé L'analyse d'une série d'échantillons de craie provenant du bassin houiller de Lublin met en évidence le fait que la porosité ouverte de la craie est élevée bien qu'elle soit peu perméable; l'eau gravitaire susceptible d'être fournie par la craie est aussi peu abondante. Par ailleurs, la porosité ouverte de la matrice crayeuse diminue avec la profondeur; ceci est dû probablement à l'augmentation de la charge lithostatique dans le même sens.

Abstract:Laboratory tests performed on 181 rock samples from boreholes drilled in different areas of the Betic Cordillera allow us to calculate their hydraulic conductivity and open porosity values. Higher values are generally associated with Miocene calcareous sandstones, although hydraulic conductivity reaches its highest values in some isolated limestone and dolostone samples. Lower values were found in marly limestones and marbles. Specific yield ranged from 0 to 0Ð0798, with a mean value of 0Ð00579. A total of 79 samples did not release water during the specific yield test, while another 11 samples released water for more than 30 min. Such wide ranges of variation show the great diversity of behaviour that the matrix of the carbonate rocks can have, referring to water storage and transfer, and its influence on pollutants spread, for example. A weak relation between interconnected porosity and hydraulic conductivity was found. The relation between interconnected porosity and specific yield is slightly stronger, except in the case of the dolomites, where a high correlation was found. No dependence on depth was found for hydraulic conductivity and interconnected porosity.