Vízügyi Közlemények, 1958 (40. évfolyam)
4. füzet - VII. Kisebb közleménye
(54) Правильно поступаем тогда, когда строго ограничивая приблизительные методы, они применяются только для таких участков, у которых приближение есть наиболее приемлимым. Таким образом для неизвестных факторов могут быть определены такие кажущиеся величины, помощью которых — имея ввиду величину опораживания депрессионной воронки и замедленного дебита воды —могут быть для коэффициента фильтрации, для горизизонтальной длины депрессионной кривой и дебита колодцев определены такие величины, которые близкие действительности (рис. 10., 14. и 15.). Более подробное резюме дается на немецком и английском языках. (Резюме автора, перевод от инж. Г. Чегиди) ON THE PRACTICAL APPLICATION OF WELL-HYDRAULICS by K. UBELL, Candidate of Technical Sciences (See pp. 306—333 of the Hungarian Text) UDC.532.544:628.112 Although the hydrodyn amical theory of seepage, which substitutes on basis of the Darcy law a fictitious phenomenon for the actual flow, may be considered well developed, results obtained thereby are in most cases of but insufficient reliability. This is due partly to the fact, that no satisfactorily accurate values are as a rule available for the coefficient of hydraulic conductivity (k , LT" 1), and partly to inaccuracies introduced into the solution by simplifying assumptions. The three-dimensional, axially symmetrical flow towards the well in case of a free groundwater table can be described but approximatingly by available mathematical methods (Fig. 1.). Actually, boundary conditions of the seepage range are, in general, known for isolated sections only. Steady flow occurs but very rarely and only under favourable conditions. Boundaries of the seepage range are, namely, in most cases, subject to continuous changes and an unsteady flow prevails either in the entire range, or ower a significant part thereof. In solving practical problems, recurrence must, therefore, still be made to approximating hydraulic methods involving simplifying assumptions and the neglect of certain factors. These methods can be classified into two different groups. Methods pertaining into the first group (those of Dupuit, Thiem, Jaeger) consider steady flow in a simplified form. The method of Dupuit is used most frequently, although the percolation surface at the well mantle is neglected therein, which constitutes the main objection against this method (Fig. 2). Owing to this neglect the method does not give a fair approximation of the actual phenomenon even in a well defined range of seepage. Actually, steady flow can generally be observed only in the immediate vicinity of the well. As a result of the various simplifying assumptions these approximating methods show the widest divergence for this very section. Over more distant sections the drawdown curve varies continuously. A single intermediate section can thus only be found on the actual drawdown curve where there is a „formal agreement" with the Dupuit formula (Figs. 3 and 9). Formulae pertaining to the second group (Weber, Kozeny, Theis, Jacob) attempt to give a fair approximation of the unsteady flow. A common feature of all is the assumption of the complete drainage of all voids in the soil, occurring simultaneously with the sinking of the groundwater table. It is assumed further, that, after a certain period the groundwater table is lowered by a uniform value throughout the entire layer. In the initial stage of pumping the water stored in the soil is drawn off and an unsteady flow is started. More detailed observation records are available for this period only. It was expected, therefore, that more definite conclusions could be made by the aid of these methods. However, more detailed investigations revealed the results to be unsatisfactory. Evaluating data obtained by three pumping tests indicated much more complex
