Określanie horyzontalnej anizotropii warunków filtracji w utworach szczelinowych na podstawie analizy nieustalonego dopływu do studzien

Abstract

EVALUATION OF HORIZONTAL ANISOTROPY OF FILTRATION CONDITIONS IN FISSURED DEPOSITS ON THE BASIS OF ANALYSIS OF UNSTABLE INFLOW TO WELLS Summary The paper presents a method of estimating horizontal anisotropy of filtration conditions in fissured rocks which is based on analysis of groundwater table observations made with the use of a set of piezometers during test pumping in well taking water from aquifer with a free table. The studies were carried out in an area built of fractured marls with two principal systems of orthogonal joint differing from one another in density and width of fractures and resulting in horizontal anizotropy of filtration conditions. Orientation and values of main components of conductivity tensor t were determined using J. S. Papadopoulos (8) formulae for aquifers with table under pressure and comprised by complete well. A mode of interpretation of the curves s = f (lgt) of drop of water table in observational wells is given. It makes possible to estimate values of instantaneous and total filtrability coeficients characterizing particular stages of drainage of aquifer with free water table. The results of estimations of these parameters made for an aquifer built of Upper Senonian marls were subsequently compared with results of field measurements of fissurity. This made it possible to state that the role of fissure system is almost completely limited to water transport whilst water storage is mainly determined by interaggregate and microfissure porosity. In concluding there are listed factors bearing a decisive influence on accuracy of estimations of hydrogeological parameters of fractured massif, carried out with the use of this method.