Hidrológiai Közlöny 1962 (42. évfolyam)

2. szám - Juhász József: Beszivárgás levegő jelenlétében

120 Hidrológiai Közlöny 1962. 2. sz. Juhász J.: Beszivárgás levegő jelenlétében uoAHHoro cTOJiöa. PacmiTaHHbie BejinniHbi (oKarae eAHHHUbl B03flYUIH0r0 CJTOH nOfl AefíCTBHeM pa3HbIX BbICOT BOAJIHORO CTOJiöa) NPIIBEAEHBI B maÖAUiie 3. MO>KHO ycTaHOBHTb, MTO OTHOCllTCJlbHO HeÖOJIbLIIOe CMOTHe B03AVXa Morjio öbi BBIACPWCATB BOAJIHUÍÍ CTOJIŐ C Bbicoroii 2—3 M. B íieficTBiiTejibHocTH ímeeTCíi OTKJiOHCHiie OT 3Toro npeanoJioweHiiíi, ÍIOTOMY MTO BO BpeMH HH(J>HJibTpaunn o6pa3yioTC>i B rpyHTe TaK Ha3bmaeMbie „rpyHTOBbie TpyÖKH", iepe3 K0T0pbie 6ojibuiaíi MacTb B03/;yxa BHXOAHT ii3 rpyHTa. CyuiHOCTi, „rpyHTOBbix TpySoK" COCTOIIT B TOM, MTO 3a HaMajibHbift yiacTOK HHtjmjibTpamm AABJIEHIIE BOAH 6Y.NET MeHbine B HaiiMeHbiniix nopax — npoABii>KeHiie BOAW B KOTOPBIX AHJIFLETCFL MEFLJIEHHBIM —, MCM B 6ojiee KpynHbix nopax, n03T0My B03Ayx HaMimaeT BbixoAHTb iepe3 OA11H H3 HHX TaK, MTO TCM CaMbIM BblTCCHHCTCÍl HaxoAamaHCH Ta.M BOfla H 33TCM nocTeneHHO noTecHHeToi. BJIAROAAPÍI TaKOMy cnocoöy BBITECHEHIW B03Ayxa H3 rpyHTa n0BHflHM0My yMCHbiiiaeTCíi KantijuiíipHaH ciiJia. HMCHHO 3TOT onbiT npiiBeji OTAEJIBHBIX iiccjieflOBaTejieíí K TAKOMY cooöpawceHHio, MTOGM npu iiHijiiiJibTpauHH He yMHTbiBajiH nojiHvio BejiHHHHy KamijijijipHoro cna^a, a TOJIBKO NEKOTOPYIO ero MACTB N TSKHM 0Öpa30M YQECTB AonojiHHTejibHOe conpoTHBJieHHe, HeoöxoAHMoe AJIH BHTecHeHHji B03Ayxa H3 rpyHTa. llOMHMO npe>KHero cnocoöa yneTa AonojiHHTejibHoro conpoTOBjieHHíi e cmarribe daemca Hoeoe rtpedAOjtcemie ÖAH eeoda (panmopa pedyKifuu A

R, KOTOPBIH ÍIBJIJICTCH OTHOUlCHIieM ACÍICTBHTejlbHOrO yKJlOHa (I

Cs) H yKJioHa (It), co3AatomerocH 6e3 conpoTiiBAeHHH B03Ayxa, HaxoAíiuierocH B rpyHTe. Bejinmina a

r onpeAejiiuiacb ABOHKO. Pa3 B TOM CJiyiae, KorAa conpoTMBjieHiie yBejiHiiiBaeTCH II B rpyHTOBOíí TpyŐKe nponopuiiOHajibHO c iiH(})njibTpauHeH [11] H Apyi'ofl pa3, KorAa BbicoTa conpoTiiBAHiomerocH BOAHHOTO CTOJiöa He yBejnmiiBaeTCH [13]. 3TH ABa nyqKa KpiiBbix MOWHO bhactb Ha ipueype 2, I ac BbicoTa BOAHHoro CTOJiöa B rpyHTOBOü TpyÖKe JIBJIHCTCH napametpom. flpil HH(J)HJlbTpailHll conpoTHBJieHHe B03Ayxa TOMHO MO>KHO ymiTbiBaTb Ha 0CH0B3HHM (fiuzypu 2. A npn6jin3iiTejibHO MO>KHO yqecTb no cpeAHefi KpiiBOÍi STIIX nyHKOB, no KOTopoíí yMeHbiueHHe iiHtJmjibTpauHOHHoii cKopocTii B cjiyiae u = 5 (B rpyHTe c BECBMA pa3HWMH 3epHaMii) a

r = 0,94, a B CJiyiae a

r = 0,84; npu u<2 (B rpyHTax c OAHHAKOBBIMII 3epHaMH) = 0,75 yniiTbiBaETCH c YMHO>I<EHNEM STHX BCJIHHHH. U MOAYJIB nepaBHOö 60 McpnocTii : , rae D — AiiaMt i P 3epHa B MM-ax. -ÖJO npedAOJiceHHbtü cnocoő pacnema MOJICHO npiiMeHumb ÖAH epynmoe om necnaHHoeo una do KpynH03epHUcmbix necKoe. B o6jiacTjix A'iaMeTpoB, npcBumaiomiix aToro jiBJieHiisi y>Ke pacxoAHTCH OT npeflnoJio>KeHHbix B TaKOíi Mepe, MTO Tam npiiweHHTb yKa3aHHbix cnocoö Hejib3íi (fla>Ke ii iipn6jiii3iiTejibH0. Infiltration in Ihe Presence of Air By Dr. J. Juhász Candidate of Teelinical Sciences The aim of the paper is to raise a few ideas on the physies of three-phase infiltration, and to suggest a method for the calculation of infiltration in the presence of air. A small part of air in groundwater was found to be present in an absorbed form, whereas a major part in an occluded state. During the investigation of three-phase seepage B. B. Lapuk established the phase-permeability in terms of the ratio of watervapour saturation of the pores (Fig. 1.). The phasepermeability of water is given by L. S. Leibenson and Averianov by Eqs. (1), (2), respectively (2/a). The results show a fair agreement with the experiments of B. B. Lapuk (Fig. l.J. The velocity of a bubble rising in groundwater can be calculated from Eq. (8), respectively (l/a) for small bubble diameters, whereas for bubbles larger than 0,04 mm Eq. (7) applies. (Informative values are given in Table 1.) From the former relatíve rising velocity the absolute rising velocity can be calculated, by taking into account the new infiltration velocity, from Eq. (8/b). (Calculated values are compiled in Table 2 for a gradient I = 1.) Water filtrating into the soil compresses the air encountered therein. The extents of compression balancing water columns of different height could be calculated from Eq. (9) if air would be prevented from escaping the pressure of water. Calculated values (the compression of the air cushion of unit thickness under water columns of different height )are compiled in Table 3. A relatively small compression of air can be seen to be sufficient for balancing a 2 to 3 m high water column. The explanation for the discrepancy between actual conditions and the above assumption is, that „soil stacks" develop during the infiltration process and the greatest part of air present in the soil escapes through these. The essential feature of „soil stacks" is that after the initial phase of infiltration the water pressure decreases in the smallest pores — in which the progress of water is slowest -— relatíve to the larger ones, and consequently the escape of water starts through one of these by displacing the water already entered and continuously forcing it back therefrom. This assumption concerning the displacement of air in the soil resulted in an apparently reduced capillary force. This experience suggested to somé investigators to take, rather than the full value of capillary suction, only a certain part thereof into consideration during the analysis of infiltration. allowing thereby for the additional resistence presented by the necessity of displacing the air in the soil. For taking care of the additional resistance a new method, the introduction of the reduction coefficient a

r is suggested. This coefficient is the ratio of the actual gradient (I

cs) and the gradient developing in the soil without the resistance of included air (It). The value of a

r has been determined by two methods : once for the case where the resistance in the soil stack increases proportionately with infiltration, Eq. (11), and then for the case where the resisting water column remains unchanged, Eq. (13). The two families of curves are plotted in Fig. 3, with the water column in the soil stack as parameter. The air resistance at infiltration can be taken into account accurately by using Fig. 3, while an approximation can be made by taking average values of the curves. Accordingly the reduction of the infiltrating velocity can be obtained by multiplication with the coefficient A

R, the value of which is 0,94 for ÍÍ > 5 (soils with a very large rangé of grain sizes), whereas for u= 3, it is 0,84, and for w< 2 (uniform grain size) a

r = 0,75. (u is the uniformity coefficient, D

e

0

:D

l

0, with D denoting the partiele diameter in mm.) The calculation method suggested can be used for soils ranging from silty sand to c.oarse sand. Phenomena taking place in particle-size ranges above and below these limits depart to such an extent from the assumed ones which proliibits the use of the method even as approximation.