Clayey barriers: compaction, hydraulic conductivity and clay mineralogy

Infiltration, swelling, and water movement were studied during ponding on a swelling clay soil. The soil was uniform in texture and clay mineralogy to 2 m depth. Most structural heterogeneity, caused by gilgai and shrinkage cracks, had been removed by grading, cultivation, and pre-ponding irrigations. Measurements were made of infiltration, moisture content, soil water potential, hydraulic conductivity, bulk density, vertical soil swelling, and the effect of overburden on tensiometer readings. Infiltration was rapid and water penetrated deeply during the first ponding day. Thereafter, qualitative agreement was found between measured infiltration and that expected from theory from 1 to 45 days after ponding. From 45 to 120 days after ponding, the development of a time-variable flow restriction near the soil surface prevented the attainment of a final, steady infiltration rate. During ponding a transient water table developed, moisture profiles were distinctly hydric, and seepage to a deep water table or aquifer was not negligible. Core sample values of hydraulic conductivity agreed with those obtained from mean flux and potential gradients, although conductivity and infiltration rate varied greatly from place to place. Measured swelling compared favourably with that calculated from bulk density changes. The maximum measured soil swelling, in the rather narrow range of moisture contents involved, was 25 mm. This is consistent with reported data on similar soils. Mean values of � = �/P near saturation at 0.2 and 0.4 m depth were between 0.20 and 0.25, indicating that the effect of overburden potential on flow was not large.

Download Full-text

Effect of Clay Mineralogy and Aluminum and Iron Oxides on the Hydraulic Conductivity of Clay-Sand Mixtures1

Clays and Clay Minerals ◽

10.1346/ccmn.1985.0330511 ◽

1985 ◽

Vol 33 (5) ◽

pp. 443-450 ◽

Cited By ~ 28

Author(s):

N. Alperovitch

Keyword(s):

Hydraulic Conductivity ◽

Iron Oxides ◽

Clay Mineralogy ◽

Aluminum And Iron Oxides

Download Full-text

INFLUENCE OF THE MICROSTRUCTURE AND MINERALOGICAL COMPOSITION ON THE LABORATORY HYDRAULIC CONDUCTIVITY OF MARLS FROM NORTHERN PELOPONNESE

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.16672 ◽

2004 ◽

Vol 36 (4) ◽

pp. 1902

Author(s):

T. Χριστοδουλοπούλου ◽

Π. Τσώλη-Καταγά

Keyword(s):

Hydraulic Conductivity ◽

Clay Minerals ◽

Pore Space ◽

Influence Factors ◽

Clay Fraction ◽

Clay Mineralogy ◽

Mineralogical Composition ◽

Microstructural Characteristics ◽

Layer Effect ◽

Swelling Clay Minerals

The role which microstructural characteristics and clay mineralogy plays on the saturated hydraulic conductivity value (k) of marls from Northern Péloponnèse, measured in the laboratory, is studied. This value must be taken under consideration when severe geotechnical problems are investigated (e.g. embankment foundations, landslides phenomena involving clayey sediments, soil conditioning e.t.c.) or empirical functions are applied to predict hydraulic conductivity from basic geotechnical properties. The marly samples were analysed by x-ray diffraction (XRD) and by thermo-gravimetric methods (DTA, TG) for the determination of mineralogical composition of clay fraction and by scanning electron microscopy (SEM) for the study of their microstructure. Their basic physical characteristics (grain-size distribution, e, WL, WP, IP, GS, Yd, n) were also determined. The coefficient of permeability (or hydraulic conductivity, k) was measured by the falling head method and the values obtained range between 1.66 10~8 and 1.06 10"6 cm/s, with a few exceptions. Our results indicate that the occurrence of swelling clay minerals in these cohesive marly sediments influences the value of hydraulic conductivity. Because of the double-layer effect not all the pore space contributes to seepage. Furthermore, the aggregation or flocculation of clay minerals and other microstructural characteristics related to the packing of structural constituents (forming an open or tight microstructure), the shape and the distribution of micropores, and the cementation degree of the microstructure are influence factors that affect the value of k. Predicting k, using empirical functions reported by several researchers for cohesive materials, or from simple correlations, as this of k versus clay fraction which is reported in this paper, is not absolutely safe, especially for cemented sediments as marls. Physicochemical factors, as the above-mentioned, play a prevalent role on the hydraulic conductivity value and they cannot be quantified and accounted in existing models.

Download Full-text

Reduction of hydraulic conductivity and loss of organic carbon in non-dispersive soils of different clay mineralogy is related to magnesium induced disaggregation

Geoderma ◽

10.1016/j.geoderma.2019.04.019 ◽

2019 ◽

Vol 349 ◽

pp. 1-10 ◽

Cited By ~ 5

Author(s):

Yingcan Zhu ◽

John McLean Bennett ◽

Alla Marchuk

Keyword(s):

Hydraulic Conductivity ◽

Organic Carbon ◽

Clay Mineralogy ◽

Dispersive Soils

Download Full-text

Sustainable and Stable Clay Sand Liners over Time

Sustainability ◽

10.3390/su13147840 ◽

2021 ◽

Vol 13 (14) ◽

pp. 7840

Author(s):

Ahmed M. Al-Mahbashi ◽

Muawia Dafalla ◽

Abdullah Shaker ◽

Mosleh A. Al-Shamrani

Keyword(s):

Hydraulic Conductivity ◽

Initial Period ◽

Clay Mineralogy ◽

Hydraulic Gradient ◽

Fine Content ◽

Wetting And Drying ◽

Fine Material ◽

Material Migration ◽

Loss Of Mass ◽

Set Up

The washout of fine materials from liners consisting of clay–sand mixtures is expected to influence the hydraulic conductivity. Clay sand liners must be assessed for efficiency when initially subjected to flood or standing water as the wetting under a hydraulic gradient can cause fine material to move and migrate away from the mixture. During wetting and drying complex expansion and shrinkage, changes take place. These changes affect the hydraulic conductivity and are likely to go out of the design range set out for the facility. The research covers the behavior of two clay sand liners tested over an extended time. The hydraulic conductivity measured under a specific hydraulic gradient was measured continuously following the establishment of the test set-up. Self-recording sensors were used to measure the temperature during the tests. The results indicated that the hydraulic conductivity reduces after an initial period of increase and fluctuation caused by the loss of mass because of fine material migration and swelling initiated due to the high content of smectite minerals. The testing and monitoring continued for more than 400 days. The permanent reduction in the hydraulic conductivity occurs after the initial period of repeated rise and fall. The extent of the initial period for the two tested mixtures is subject to the fine content mass and the clay mineralogy. The continuous reduction in the hydraulic conductivity after the initial period is due to the rearrangement of particles and compression in the sand–clay mixture.

Download Full-text