Coupled chemical-hydraulic-mechanical behaviour of bentonites

Dominijanni, Andrea; Manassero, Mario; Puma, Sara

doi:10.1680/bcmpge.60531.005

Cited by 9 publications

(36 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For a GCL specimen with n of 0.86, ω ranged from 0.08 to 0.42 for C avg ranging from 23.5 to 4.4 mM KCl. The higher values of ω reported in this study relative to those of Malusis and Shackelford (2002a) and others (e.g., Dominijanni et al, 2013; Malusis et al, 2014; Meier et al, 2014) are probably due to the increased percentage of Na + on the exchange complex of the bentonite due to the dialysis homo‐ionization procedure performed as part of the specimen preparation.…”

Section: Example Resultscontrasting

confidence: 62%

“…Several testing systems have been reported for measuring semipermeable membrane behavior of clayey soils (e.g., Letey et al, 1969; Olsen, 1969; Whitworth and Fritz, 1994; Keijzer et al, 1997, 1999; Malusis et al, 2001; Shackelford and Lee, 2003; Shackelford, 2011, 2013; Dominijanni et al, 2013). These testing systems can be categorized as either open or closed systems, as illustrated schematically in Fig.…”

Section: Laboratory Measurement Of Membrane Efficiencymentioning

confidence: 99%

“…The traditional, through‐diffusion method of analysis has been used to determine D * values of saturated clays and clay mixtures in multiple studies using closed‐system experiments to evaluate coupled diffusion and semipermeable membrane behavior (e.g., Malusis and Shackelford, 2002b; Di Emidio, 2010; Dominijanni et al, 2013; Malusis et al, 2014; Bohnhoff and Shackelford, 2015):

D^{*} = - (\frac{L}{θ (C_{b, avg} - C_{t, avg})}) J_{d, ss}

where L is the length of the specimen, θ is the volumetric water content of the specimen, and J d,ss is the diffusive mass flux ( J d ) at steady‐state diffusion through the system. Note that θ is defined as the product of the specimen porosity, n , and S (i.e., θ = nS ), such that θ = n when the specimen is saturated.…”

Section: Testing Proceduresmentioning

confidence: 99%

See 2 more Smart Citations

Apparatus for Measuring Coupled Membrane and Diffusion Behavior of Unsaturated Sodium Bentonite

Sample-Lord¹,

Shackelford

2017

Vadose Zone Journal

View full text Add to dashboard Cite

Sodium bentonite (Na-bentonite) has been shown to exhibit semipermeable membrane behavior-the ability to selectively restrict the migration of dissolved chemical species through the pores of the clay. However, experimental research to date has focused on the membrane behavior of Na-bentonite almost exclusively under water-saturated conditions (i.e., degree of saturation S = 1), even though membrane behavior under unsaturated conditions is expected to be more significant. Further, the limited number of studies that have been performed to evaluate membrane behavior in unsaturated soils have used only open systems to quantify membrane efficiency (w), despite the testing advantages of using closed systems (e.g., more accurate measurement of w, easier control of boundary conditions). Thus, a closed-system testing apparatus capable of measuring coupled membrane and diffusion behavior in unsaturated Na-bentonite was developed and then used to measure w and salt diffusion in Na-bentonite with S of 0.84 and 1.0. For a source solution (concentration difference) of 20 mM KCl, w increased from 0.61 to 0.71 as S decreased from 1.0 to 0.84, which is consistent with the current conceptual understanding of membrane behavior and trends in the literature. In contrast, the effective diffusion coefficient for Cl − was essentially the same (i.e., ?1.8 ´ 10 −10 m 2 s −1 ) for both specimens due to the small difference in S. The development of the testing apparatus advances the state of the art for laboratory measurement of coupled membrane and diffusion behavior in unsaturated clays commonly used as chemical containment barriers.Abbreviations: DIW, deionized water; EC, electrical conductivity; GCL, geosynthetic clay liner; HAE, high air entry; IC, ion chromatography; ICP-AES, inductively coupled plasmaatomic emission spectrometry.High-activity clays such as Na-bentonites are commonly used as barrier materials in chemical containment applications (e.g., landfills, radioactive waste disposal, animal waste lagoons, mine tailings containment). These clays also have been shown to behave as semipermeable membranes, whereby dissolved chemical species (solutes) in the pore water are selectively restricted from passage through the clay (e.g., Shackelford, 2013). Because the primary objective of chemical containment barriers is to reduce the rate and extent of migration of chemicals into the surrounding environment, the existence of semipermeable membrane behavior can enhance the containment function of the barrier . As a result, significant research focused on characterizing membrane behavior in a variety of clay barriers commonly used in chemical containment applications has been conducted during approximately the past 20 yr (e.g

show abstract

Section: Example Resultscontrasting

confidence: 62%

Section: Laboratory Measurement Of Membrane Efficiencymentioning

confidence: 99%

D^{*} = - (\frac{L}{θ (C_{b, avg} - C_{t, avg})}) J_{d, ss}

Section: Testing Proceduresmentioning

confidence: 99%

See 1 more Smart Citation

Apparatus for Measuring Coupled Membrane and Diffusion Behavior of Unsaturated Sodium Bentonite

Sample-Lord¹,

Shackelford

2017

Vadose Zone Journal

View full text Add to dashboard Cite

show abstract

“…In addition to the measurement of the reflection coefficient, the laboratory apparatus where L is the length of the specimen, n is the soil porosity, and ( ) s ss J is the salt mass flux 200 measured under steady-state conditions. 201 Dominijanni and Manassero (2012b) and Dominijanni et al (2013) where τ m is the dimensionless matrix tortuosity factor, which accounts for the tortuous nature of the 208 diffusive pathways through the pores that are accessible to the solute, τ r is the restrictive tortuosity…”

mentioning

confidence: 99%

“…The swell coefficient, ϖ, was introduced by Dominijanni andManassero (2012a, 2012b) to 219 quantify how efficient a change in the salt concentration of the equilibrium solution is at producing 220 a variation in the chemico-osmotic swelling pressure, u sw , which develops in response to the ion 221 partition mechanisms that occur within the semipermeable porous medium. The coefficient ϖ,…”

mentioning

confidence: 99%

Laboratory assessment of semi-permeable properties of a natural sodium bentonite

2018

View full text Add to dashboard Cite

The relevance of the semi-permeable properties of bentonites, which affect both their transport processes and mechanical behaviour, has been assessed through the experimental determination of three parameters: the reflection coefficient, ω; the osmotic effective diffusion coefficient, [Formula: see text]; and the swell coefficient, ϖ. Two multi-stage tests were conducted on a natural sodium bentonite, while varying both the specimen void ratio, e, and the solute concentration, cs, of the equilibrium sodium chloride (NaCl) solutions. The measured phenomenological parameters were interpreted through a mechanistic model, in which the electric charge of clay particles is taken into account via a single material parameter, [Formula: see text], referred to as the “solid charge coefficient”. A constant value of [Formula: see text] = 110 mmol/L was found to provide an accurate interpretation of the experimental data, at least within the investigated range of bentonite void ratios (3.33 ≤ e ≤ 4.18) and NaCl concentrations of the external bulk solutions (5 ≤ cs ≤ 90 mmol/L). The results support the hypothesis that both chemical osmosis and swelling pressure are macroscopic manifestations of the same interactions, which occur at the microscopic scale between the clay particles and the ions contained in the pore solution, and that both of them can be modelled through a single theoretical framework.

show abstract

Semipermeable membrane behavior of geosynthetic clay liners

Shackelford

Scalia

2022

IOP Conf. Ser.: Mater. Sci. Eng.

View full text Add to dashboard Cite

The focus of this paper is on providing an overview of the results of the nearly 20 years of research related to the discovery, examination, and potential benefits of semipermeable membrane behavior of bentonite-based geosynthetic clay liners (GCLs) commonly used as barriers or components of barriers in a variety of hydraulic and chemical containment applications, such as water and chemical retention ponds, tailings and coal ash impoundments, and solid waste landfills. First, the concept of solute restriction underlying semipermeable membrane behavior and the development of a solute-restriction or membrane efficiency coefficient (ω) and chemico-osmosis (q π) are described. Second, previously measured values of ω are presented for clays and GCLs for the purpose of illustrating the physical and chemical factors affecting ω. Third, the potential benefits of both ω and q π in terms of hydraulic and chemical containment applications are illustrated, and the relative importance of ω versus q π is described. Finally, some of the remaining issues related to the semipermeable membrane behavior of GCLs, such as the uniqueness of the measured ω and the persistence of ω at high salt concentrations, are discussed.

show abstract

Coupled chemical-hydraulic-mechanical behaviour of bentonites

Cited by 9 publications

References 20 publications

Apparatus for Measuring Coupled Membrane and Diffusion Behavior of Unsaturated Sodium Bentonite

Apparatus for Measuring Coupled Membrane and Diffusion Behavior of Unsaturated Sodium Bentonite

Laboratory assessment of semi-permeable properties of a natural sodium bentonite

Semipermeable membrane behavior of geosynthetic clay liners

Contact Info

Product

Resources

About