MEASURING HYDRAULIC CONDUCTIVITY IN CLAY SOILS

Publisher Website
Google Scholar
Abstract
A standard method for determining hydraulic conductivity of packed, fragmented material has been evaluated for clay soils, 15 in all, covering a range of water stability and degree of swelling. The particular method tested is a comparative, or analogue- type, measurement, widely used in irrigation capability studies; in some circumstances it can have direct application to cultivated soils. The data are presented, along with related soil properties, with the results for three nonclay soils for comparison. The value of divided outflow permeameters for measurement in both soil cores and fragmented material was also investigated; theoretically this method allows correction for wall flow, or for the effects of deformation near the wall when the soil swells. Eacn method is commonly regarded as furnishing the saturated hydraulic conductivity, but analysis of data from the two methods makes it clear that this is not always so, particularly for soils of low stability. Even so, the standard method is considered to be useful in assessing the suitability of surface soils for irrigation. The results obtained with the divided outflow permeameters were equivocal, but the method probably gives more reliable results for core samples by correcting for wall flow. Equivalent hydraulic conductivity values were obtained with constant-head and falling-head techniques, except very early in an experiment. Replacement of air with carbon dioxide in the packed soils, before application of water, reduced variability and made experimentation more tractable. The effect of covaring the surface of the soil with sand, a variation sometimes used to alleviate slaking and dispersion, depended strongly on the nature of the soil and is not recommended. Examination of instrument and measuring errors showed that these could be large, but statistical analysis of the data indicated a relatively low between-sample variability of the measured hydraulic conductivity and other properties of the packed soil.

This publication has 0 references indexed in Scilit: