|Reference : Recherches expérimentales sur la filtration et la pénétration de l'eau dans le sable et ...|
|Scientific journals : Article|
|Engineering, computing & technology : Geological, petroleum & mining engineering|
|Recherches expérimentales sur la filtration et la pénétration de l'eau dans le sable et le limon|
|[en] Experimental Research on Filtration and Water Penetration into Sand and Silt|
|Spring, Walthère [Université de Liège - ULg]|
|Annales de la Société Géologique de Belgique|
|Société Géologique de Belgique|
|[en] Filtration ; Waters, natural ; Sand ; Silt|
|[fr] Filtration ; Eaux naturelles ; Sable ; Limon|
|[en] Spring, W. Annales de la Societe; geologique de Belgique; Memoires (1902), 29, 17-48; SciFinder (Chemical Abstracts Service: Columbus, OH); https://scifinder.cas.org (accessed July 8, 2010).
In the experiments iron hydroxide was removed from sand by HCl by, subsequently the sand was boiled off with water and under water filled into 2 cm wide glass tubes. The tubes were sealed by an bored-through stopper provided at the lower, rear end a thin wire gauze and eventually a thin cotton wool plug, and the outflow tube pushed into the same leads into a container with water under constant pressure; the other tube end was provided with an inlet tube, which was also connected also to a water container under constant pressure. During off-time of the experiments the tubes were sealed air-proof. Both the tubes and the container intended for the in-take of the water flowed through were placed beside each other and were subjected thus in same way to the by the way almost constant temperature. An indispensable condition for the success of the experiments is the uniform grain size of the sand, which by the way may be put into the tubes only by small amounts. The substantial results of these investigations touching different hydrologic and soil science controversial issues are the subsequent: 1. The velocity of water circulating in horizontal direction in a sand does is not in reverse relation to the thickness of the filter and in straight relation to the applied pressure. In thick filter columns the pressure effect decreases more and more, and the movement of the water is only based on the imbibition. The effect even of a very strong pressure stops after short extending, and the water flows, as if no pressure was applied, therefore a pressure locally applied on a sand layer does not propagate on a considerable distance. 2. With the filtration in vertical direction according results are obtained only for same particle size of the sand; since this condition in nature is hardly fulfilled, no generally valid mathematical formula can be set up for this circulation. Under influence of the water movement in vertical direction the fine parts of the sand move upward, so that the water passage is hindered here and a to a certain extent an automatic rational filter is formed. 3. The resistance of the filter exerted on the passed water decreases apparently proportional to the filter thickness, the POISEUILLE law is only valid for thin filters. 4. If the water percolating the sand filter contains air, so it sticks at the sand grains on certain positions and hinders to a high degree the descending of the water. 5. The runoff from a vertically placed filter decreases only proportional to the thickness at the point, when the pressure reached a certain intensity. If this pressure is only weak, then the filtrate quantity increases with the filter thickness, because then the weight of the water column makes an effect. From this the conclusion is to be drawn that the seepage water quantities supplied to a groundwater stream are not pressed down by any means by the thickness of the layer to be percolated. 6. The volume of the water moistening the sand predominates the volume of the voids of the sand grains in apparent contact the more, the finer the sand is. The free space between the sand grains influnces therefore enormously the mobility of the sand impregnated with water (swimming sand). 7. Temperature increase accelerates the action of a filter due to the reduction of the inner friction of the filter fluid, however for a doubling of the filtrate quantity a rise in temperature to almost 30° is required. 8. The loess loam from the Hesbaye is still permeable for water at a thickness of 8 m (and probably still further). The same applies to clay, as long as he does not stand under pressure, thus it can be unhinderedly expanding correspondingly to the infiltration. 10. From all that it follows that the down flow of the meteoric water cannot take place regularly through the soil in parallel layers. Flowing on into the depth takes place only in limited space, because of the soil air which has to be displaced, since channels must remain for escaping air. Here the water penetrates only if the surface is sprinkled or covered by a rather high water layer or by melting snow, respectively. If the water begins to penetrate, then its velocity increases with the height of the water column. Subsequently on the superficial layers a suction effect is then carried out, which stops only then if the flow downward is in equilibrium with the capillary impregnation, and so the movement is downward annihilated.
Reprinted with the permission of the American Chemical Society. Copyright © 2010. American Chemical Society (ACS). All Rights Reserved.
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