Vízügyi Közlemények, 1969 (51. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(46) The most important feature is the extremely high (10,000 to 55,000 mg/litre) sulphate content, the relatively high (250 to 2,500 mg/litre) chloride content and the water assumed a glauber-, or bitter-salt character. The principle underlying the exploration was that the electric resistance of the soil in the above areas containing mineral water is considerably lower than in the surrounding formations containing fresh water. Measurements of soil resistance were actually performed using the probe arrangement by Schlumberger. In most of the formations the vertical-variations in resistance were low, which greatly simplified evaluation. The main characteristics of mineral-water occurrences have been compiled in Table II. In the area designated by No 1 the results of resistance measurements are illustrated by the iso-ohm maps, on which two resistance anomalies of considerable extent can be detected. These anomalies indicate the areas and boundaries thereof, in which mineral water of the required concentration is contained. The positive area characterised by the low resistance values thus demonstrated, largely coincides with that already explored and in part exploited. However, in many places it extends beyond the present productive areas, offering thus new possibilities for exploitation and a differentiated indication of the formation boundaries, on the basis of which the limits of the protective area can be traced. In the area designated by No. 2 the iso-ohm curves constructed from measurement results gave indications for the positioning of exploration boreholes, by which additional formations containing highly concentrated mineral water could be disclosed. The concentration of mineral water found in two of the boreholes not only attained but even exceeded that of the known occurrences. In the area designated as No. 3, measurement results indicated the presence of a mineral-water formation extended in north-west to south-east direction offering the possibility for sinking new exploratory boreholes, the development and extension of the productive area, i.e., for increasing the available mineral-water resources. TRACER EXPERIMENTS IN KARSTIC ROCKS By István Sárváry, Civ. Engr. (For the Hungarian text see pp. 218) The investigations described have been performed in the part of Hungary lying west of the Danube, in the area of the Dorog coal-mines. In the area of this basin the carboniferous formation and the Triassic dolomite base rock containing karstic water under pressure are not everywhere separated by a protective layer thick enough to provide a safe barrier between the water and the mine workings. In some instances the projective layer is too thin and weakened by tectonic movements, provoking the danger of water inrush. For planning the operations to exclude inrush water it is necessary to determine the direction and velocity of karstwater flow. Fluoresceine of industrial quality has been used as tracer material, which was introduced through an observation borehole. The rate of feeding was 200 litres/min for 10 days. Water containing tracer material appeared first after 49 days in the mine at a point 426 metres distant from the point of introduction, but at more distant points it could be detected even 3 months later, of course at much lower concentrations. In evaluating data the geometry of continuously operating well-like sinks, resp. sources was adopted as basis of computation, omitting the values commonly used in well hydraulics, such as hydraulic gradient, friction loss, etc. The average velocity estimated for straight-line flow and the corresponding discharges were used to determine the zones of higher velocities that formed around the boreholes and the points of water inrush. On the basis of velocity distribution the time of residence spent in the high-velocity zones can be determined, while the velocity of spontaneous flow of karstic water is found by several steps of successive approximation.