engleski

Comparison of the hydraulic conductivities calculated from pumping tests and discontinuities in the middle Eocene flysch basin, exploitation field Sv. Juraj-Sv. Kajo, Croatia

This paper contains theoretical and practical basics of geomechanics and hydrogeology, which were the basis for the estimation of rock masses' hydrogeological parameters. Focus is laid on the interpretation of geomechanical and structural data, and the mode of their use in hydrogeologic investigations, i.e. the question is: is it possible to obtain reliable hydrogeological parameters without pumping tests, just from the properties of discontinuities? Such multi-disciplinary investigations present an opportunity for collaboration and sharing of data and skillsets. The evaluation was performed on the location of the exploitation field “Sv. Juraj – Sv. Kajo” (Croatia), based in the middle Eocene flysch basin. Through field surveys data about discontinuities features were obtained, which were then analyzed and used in an idealized groundwater flow model, with the aim of determining the value of hydraulic conductivity. By interpreting the data from all measuring spots, sets of discontinuities were determined within calcarenite and calcisiltite lithological units, in which the median values of their geometrical characteristics were applied. Spacing, fracture aperture and JRC values of each individual set were used to determine values of hydraulic conductivity with the cubic law (description of groundwater flow through fractures). The comparison of theoretical results (hydraulic conductivities calculated from fracture properties) with traditional hydrological field survey results (data obtained from pumping tests) showed obvious congruence. Differences in results are a consequence that the pumping tests data are obtained at a local scale and include only the immediate vicinity of the boreholes, while in hydrogeological predictions, groundwater flow must be examined on a larger scale for reliable results. In addition, the interpretation of local scale fracture data for characterising the wider fracture network and determining the major sets of discontinuities in controlling groundwater flow is not always straightforward. However, difference in one order of magnitude is acceptable for the first and preliminary estimates of the quantity of groundwater flow.

hydraulic conductivity; discontinuity; pumping test; cubic law

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