GEOLOGOS 6 (2003) PL ISSN 1426-8981 · ISBN 83-89629-03-8 Research of hydraulic conductivity coefficient of aquitadrs in cylinders MAREK MARCINIAK 1 , JAN PRZYBYŁEK 1 , JADWIGA SZCZEPAŃSKA 2 , JANUSZ HERZIG 2 1 Adam Mickiewicz University, Maków Polnych Str. 16, 61-606 Poznań 2 University of Mining and Metallurgy, Mickiewicza Ave. 30, 30-059 Kraków Abstract: Results of field and laboratory research on the hydraulic conductivity coefficient of near-surface aquitards are presented in the article. The research was conducted for Quaternary tills and Tertiary clays occurring in the area of the Wielkopolski National Park. Special cylinders equipped with a sealing device and a contact sensor of the water level position each were designed. The cylin- ders were sunk into the examined aquitards and then injected with water. After sealing the cylinder the air inside was compressed which caused water injection from the cylinder into the examined aquitards. The rate of the injection was observed by measuring the water level depression in the cylinder. Theoretical consideration has been carried out and an own algorithm enabling computation of the hydraulic conductivity coefficient value on the basis of measurements of: depression s, time t, pressure in the cylinder ΔH and effective porosity of the examined bodies n e has been developed. During the field research a methodolo- gy of determination of the hydraulic conductivity coefficient k of near-surface aquitards was developed. 25 values for the tills and 12 values for the clays were determined. Laboratory research on the hydraulic conductivity coefficient of till and clay samples taken from the sites of the field examinations has been conducted. The results obtained during the field research have been compared to those of the laboratory research. The hydraulic conductivity coefficient values resulting from the laboratory research are by two orders of magnitude lower than those of the field research. It has been found that sample consolidation, essential for con- ducting the laboratory research, leads to the destruction of the system of micro- cracks and fractures occurring in natural conditions. As a result the hydraulic conductivity coefficient values obtained in laboratory conditions are lower than those obtained through field research. Field and laboratory research carried out according to the proposed methodology permit determining the variability range of the hydraulic conductivity coefficient of the examined aquitards. The upper limit of this range is constituted by the transmissivity of the system of micro- cracks and fractures and the lower limit by the transmissivity of the consolidat- ed bodies. In this sense field and laboratory research can complement each other,