Compacted expansive soils are widely used as engineered barriers in waste contaminant applications like landfills, brine ponds, and nuclear waste disposal sites. These liners are designed for very low hydraulic conductivity (&lt;1 × 10−7 cm/s). Percolation of chemical waste or leachate results in physicochemical changes in compacted expansive soils which increases the hydraulic conductivity. This paper brings out the changes in swelling behavior and hydraulic conductivity of compacted expansive soil induced with osmotic gradients using NaCl and CaCl2 solutions. Multiple identical soil specimens placed in oedometer assemblies were inundated with distilled water, 0.4 and 4 M NaCl (monovalent cations), and 0.4 and 4 M CaCl2 (divalent cations) salt solutions and allowed to swell under a surcharge pressure of 12.5 kPa. Void ratio–water content plots were also traced during swelling process. Falling head permeability tests were conducted on swollen soil specimens in rigid wall oedometer permeameters under a hydraulic gradient (i) of 20. The experimental results showed that the swell potentials reduced and hydraulic conductivity increased with the increase in induced osmotic suction. © Springer Nature Singapore Pte Ltd 2019.

T. Thyagaraj

Department Of Civil Engineering

M. Julina

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Effect of Induced Osmotic Suction on Swell and Hydraulic Conductivity of an Expansive Soil

Lecture Notes in Civil Engineering

Physico-chemical effects have a significant impact on the behavior of clay barriers due to the interactions between the pore fluid and clay particles, and they pose a great challenge because the efficiency of clay barriers and cover systems may be altered. Therefore, this paper highlights the effect of physico-chemical factors on shrinkage behavior of compacted expansive clay. To achieve this, the compacted clay specimens were inundated with distilled water, NaCl, and CaCl2 salt solutions in separate oedometer cells at a vertical pressure of 6.25 kPa and allowed to swell. The swollen specimens were gradually shrunk until the specimens attained constant mass, and the changes in void ratio and water content were monitored during drying. The experimental results showed that magnitude of induced osmotic suction and type of pore fluid had a significant impact on shrinkage behavior of compacted clay specimens due to the changes in soil structure. The average pore size of compacted specimens significantly decreased with the induced osmotic suction due to the reduction in size of micropores owing to the suppression of double layers. The discussions are supported by scanning electron microscopy images. Also, the experimental shrinkage data were fitted using modified van Genuchten and Fermi mathematical models, and the results showed that these models fit well with an adjusted R2 higher than 0.9962. © 2016 American Society of Civil Engineers.

International Journal of Geomechanics

Physico-chemical effects on shrinkage behavior of compacted expansive clay

Unsaturated clays are subject to osmotic suction gradients in geoenvironmental engineering applications and it therefore becomes important to understand the effect of these chemical concentration gradients on soil-water characteristic curves (SWCCs). This paper brings out the influence of induced osmotic suction gradient on the wetting SWCCs of compacted clay specimens inundated with sodium chloride solutions/distilled water at vertical stress of 6.25 kPa in oedometer cells. The experimental results illustrate that variations in initial osmotic suction difference induce different magnitudes of osmotic induced consolidation and osmotic consolidation strains thereby impacting the wetting SWCCs and equilibrium water contents of identically compacted clay specimens. Osmotic suction induced by chemical concentration gradients between reservoir salt solution and soil-water can be treated as an equivalent net stress component, (pπ) that decreases the swelling strains of unsaturated specimens from reduction in microstructural and macrostructural swelling components. The direction of osmotic flow affects the matric SWCCs. Unsaturated specimens experiencing osmotic induced consolidation and osmotic consolidation develop lower equilibrium water content than specimens experiencing osmotic swelling during the wetting path. The findings of the study illustrate the need to incorporate the influence of osmotic suction in determination of the matric SWCCs. © 2010 ASCE.

Journal of Geotechnical and Geoenvironmental Engineering

Influence of osmotic suction on the soil-water characteristic curves of compacted expansive clay

Géotechnique

Double-structure effects on the chemo-hydro-mechanical behaviour of a compacted active clay

Carbonates and Evaporites

Influence of the bentonite on the consolidation behaviour of soil–bentonite mixtures

Swelling of compacted clay under osmotic gradients

Effect of induced osmotic suction on swell and hydraulic conductivity of an expansive soil

Journal	Data powered by TypesetLecture Notes in Civil Engineering
Publisher	Data powered by TypesetSpringer
ISSN	23662557
Open Access	No