Vízügyi Közlemények, 1961 (43. évfolyam)

4. füzet - IX. Képek a Föld különböző részeinek vízépítési munkáiról

sure is shown to develop in the lower part, adjacent to the well mantle, of the capillary fringe, from which water can enter into the well. Thus in the vicinity of the well the corresponding section of the drawdown curve is actually situated'slightly higher. Consequently, the free seepage surface along the well mantle consists essentially of two parts: those below and above Lhe drawdown curve. A further interesting condition arises when, e. g. owing to the presence of a clay layer, the free seepage surface within lhe capillary fringe becomes separated from the part lying below the drawdown curve (Fig. Ï5). It is pointed out by the author, that the gas absorbing capacity of the capillaryfringe is considerably higher than that of the groundwater lying "below the drawdown surface, which may result in the separation of iron and"lime and even in lhe deterioration of the well" mantle. For computing the free seepage surface along lhe well mantle, and the total well yield increased by the capillary discharge Eqs. (5) and (17), respectively, have been derived by the author. (For notations see Fig. 11.) Data of the model well divided by sloping baffles into several parts, i. е., lhe distribution of the discharge along the height of the well mantle are shown in Fig. 15. As will be perceived, lhe capillary discharge entering into the well can always be determined in a quantitative manner as well. Effects of the capillary fringe above the free groundwater table on the water level of actual wells drawing on lhe groundwater are studied in detail in the paper. The observed fact, that the water level in groundwater wells rises often positively to above the free groundwater table, can be traced back to the discharging capa'ciLy of the capillary fringe. In cases where the thickness of the soil layer above the free groundwater table is smaller than the height of lhe capillary rise, the existence of capillary water movement can be well illustrated by sprinkling a dye on Lhe ground surface (Fig. 20). The significance of this case lies in the fact, that in many instances (e. g. seepage írom irrigation canals) the capillary fringe emerges to the ground surface — it is so to say short-circuited as regards evaporation — and evaporation losses become appreciably higher. Attention is called finally to the fact, that similarly to scale model testing in general, also in lhe case of free-surface seepage movement, scale effects due to the influence of lhe capillary fringe should be taken into consideration. Results of investigation into the capillary fringe will be published in the near future in connection with other aspects (e. g. irrigation, waterhousehold). Author's summary translated by Z. Szilvássy struct, eng. EFFET DE LA FRANGE CAPILLAIRE SUR LES PHÉNOMÈNES DE FILTRATION À SURFACE LIBRE Par G. Öllős (voir texte hongrois pp. 127) L'étude de l'hydraulique de la frange capillaire au-dessus de la nappe aquifère à surface libre est important des points de vue de l'irrigation, des bilans hydrauliques, des fondations, de la mécanique du sol et des essais sur modèles. C'est le mouvement d'eau capillaire en direction verticale que la manière de voir actuelle prend généralement en considération (fig. 1). L'auteur étudie en détail le cas, lorsque dans la frange capillaire l'eau est en mouvement au-dessus de la nappe d'eau souterraine en pente vers le point à potentiel plus petit aussi. Les constatations auxquelles l'étude aboutit se rapportent en premier lieu aux effets capillaires se produisant dans les essais sur