An influence of changing the humic acids content on soil water repellency and saturated hydraulic conductivity was studied on soil samples of Mollic Gleysol from Cilizska Radvan in the Danubian Lowland. Water repellency was measured with the water drop penetration time (WDPT) test on original soil samples and on soil samples with increased humic acids content. Saturated hydraulic conductivity coefficient was measured on the above-mentioned samples with falling head permeameter. From the results of measuring it follows that an increasing of humic acids content in soil resulted in an decreasing of the coefficient of saturated hydraulic conductivity of the soil under study. Original soil was non-water reppelent soil. Already a small increasing of humic acids content in soil (in 17.9 % at original amount) caused that the soil became slightly or strongly water repellent in the average of soil moisture 15-30 %. At soil moisture less than 15 % time of penetration decreased probably as a result of shrinking and cracking of the soil. Water repellency of soil samples from horizon 0 - 5 cm was usually higher than water repellency of soil samples from horizon 5 - 10 cm both in case of humic acids extracted from peat and in case of humic acids extracted from the same soil from Cilizska Radvan. and Na pôdnej vzorke čiernice glejovej (ČA G) (MKSP, 2000) z lokality Čiližská Radvaň v Podunajskej nížině bol skúmaný pomocou testu času vsaku kvapky vody (WDPT test) vplyv zmeny obsahu humínových kyselin na vodoodpudivosť a nasýtenú hydraulickú vodivosť pôdy. Vodoodpudivosť bola meraná na pôvodných pôdnych vzorkách a vzorkách zo zvýšeným obsahom humínových kyselín. Koeficient nasýtenej hydraulickej vodivosti bol meraný na týchto pôdnych vzorkách metódou premenlivého hydraulického sklonu. Z nameraných výsledkov vyplýva, že nárast obsahu humínových kyselín v pôde mal za následok pokles koeficientu nasýtenej hydraulickej vodivosti študovanej pôdy. Už malé zvýšenie obsahu humínových kyselín v pôde (o 17,9 % pôvodnej hodnoty ) spôsobilo, že pôda sa stala slabo až silne vodoodpudivou vo vlhkostnom rozsahu 15-30 %. Pri pôdnej vlhkosti nižšej ako 15 % sa čas vsakovania zmenšil pravdepodobne v dôsledku zmršťovania pôdy a vzniku puklín. Vodoodpudivosť pôdnych vzoriek z horizontu 0 - 5 cm vo väčšine prípadov bola vyššia než vodoodpudivosť pôdnych vzoriek z horizontu 5 - 10 cm aj v prípade pridania humínových kyselín, extrahovaných z rašeliny, aj v prípade pridania humínových kyselín, extrahovaných z tej istej pôdy.
A large single-ring infiltrometer test was performed in order to characterize the saturated hydraulic conductivity
below an infiltration basin in the well field of Lyon (France). Two kinds of data are recorded during the experiment:
the volume of water infiltrated over time and the extension of the moisture stain around the ring. Then numerical
analysis was performed to determine the saturated hydraulic conductivity of the soil by calibration.
Considering an isotropic hydraulic conductivity, the saturated hydraulic conductivity of the alluvial deposits is estimated
at 3.8 10–6 m s–1. However, with this assumption, we are not able to represent accurately the extension of the moisture
stain around the ring. When anisotropy of hydraulic conductivity is introduced, experimental data and simulation results
are in good agreement, both for the volume of water infiltrated over time and the extension of the moisture stain.
The vertical saturated hydraulic conductivity in the anisotropic configuration is 4.75 times smaller than in the isotropic
configuration (8.0 10–7 m s–1), and the horizontal saturated hydraulic conductivity is 125 times higher than the vertical
saturated hydraulic conductivity (1.0 10–4 m s–1).
The aim of this paper is to define the correlation between the geometry of grains and saturated hydraulic conductivity of soils. The particle shape characteristics were described by the ζ0C index (Parylak, 2000), which expresses the variability of several shape properties, such as sphericity, angularity and roughness.
The analysis was performed on samples of four soils, which were characterised by the same grain size distribution and extremely different particle structure. The shape characteristics varied from ideally spherical, smooth grains (glass microbeads
GM) to highly irregular and rough particles (fly ash FA).
For each soil, laboratory tests of saturated hydraulic conductivity (constant head test CHT and falling head test FHT) were performed. Additionally, an empirical analysis of effective pore diameter was conducted with use of the analytical models developed by Pavchich (Wolski, 1987) and Indraratna and Vafai (1997). The models were modified by introducing the ζ0C index.
Experiments have shown that saturated hydraulic conductivity depends on grains shape and surface roughness. This parameter decreases with the increase in the irregularity of soil particles. Moreover, it was proven that the ζ0C reflects the relationship between effective pore diameter and grain shape characteristics.
A numerical model of the unsaturated water movement in capillary pores of soil matrix was used for the water flow in macropores and in capillary pores. Hydraulic conductivity dependance on soil moisture content for macropores was linearized between two soil moisture contents: the saturated soil matrix moisture content and the saturated soil moisture content with macropores. The second one is neither possible to define unambiguously nor measure. It is possible to determine its optimal value from the measured moisture content courses and by those, calculated by mathematic model. and Na výpočet pohybu vody v dvoch oblastiach, v makropóroch a kapilárnych póroch bol použitý numerický model pohybu vody v kapilárnych póroch vodou nenasýtenej pôdnej matrice. Závislosť hydraulickej vodivosti od vlhkosti pôdy pre makropórovú oblasť bola linearizovaná medzi dvoma vlhkosťami pôdy: vlhkosťou vodou nasýtenej pôdnej matrice a vlhkosťou vodou nasýtenej pôdy aj s makropórmi. Poslednú z týchto dvoch nemožno jednoznačne definovať ani namerať. Z priebehov vlhkostí vo vybraných hĺbkach pôdy určených meraním a matematickým modelovaním môžeme určiť optimálnu hodnotu vlhkosti vodou nasýtenej pôdy aj s makropórmi.
The influence of the size soil aggregates derived from loess, expressed by mean weight diameter of aggregates which build soil samples, on the saturated hydraulic conductivity was presented. It has been found that size of aggregates influenced the amount of large pores in soil samples. The relationship between the saturated hydraulic conductivity and the amount of large pores can be described by function: Ks = 0.356. Exp (6.852 PL). and Príspevok obsahuje výsledky výskumu vplyvu velkosti agregátov pôdy, z ktorých sú vytvorené vzorky pôdy, na hydraulickú vodivost vodou nasýtených vzoriek pôdy. Z výsledkov vyplýva, že velkost agregátov pôdy ovplyvnuje množstvo velkých pórov vo vzorkách pôdy. Závislost medzi hodnotami nasýtenej hydraulickej vodivosti pôdy a množstvom velkých pórov - udaným v percentách objemu všetkých pórov - môže byt vyjadrená exponenciálnou funkciou.