Predicting the swelling pressure of MX-80 bentonite

Navarro, Vicente; Morena, Gema De la; Yustres, Ángel; González-Arteaga, Jesús; Asensio, Laura

doi:10.1016/j.clay.2017.08.014

Cited by 30 publications

(9 citation statements)

References 31 publications

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“…The latter concentration corresponds to the sodium cations in exchange positions compensating q. CCl,m for each of the macrostructural salinities were calculated (see Fig. 4), assuming an average mineral density, mineral, of 2780 kg/m 3 (Navarro et al, 2017), and considering two CEC values, 0.996 and 0.83 molc/kg (Table 1). In all cases exposed in Fig.…”

Section: Mo Mnccmentioning

confidence: 99%

Molecular dynamics data for modelling the microstructural behaviour of compacted sodium bentonites

Navarro

Yustres

Jenni

et al. 2021

Applied Clay Science

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The water content of a bentonite at low saturation (equal to high suction) defines the void ratio of the nano-scale porosity located in the clay interlayers and close to the clay grain surfaces. However, the measured suction curves should not be extrapolated straightforwardly to lower suction values, because, in that case, the presence of water in larger pores between aggregates can be non-negligible. This work analyses the use of data obtained from molecular dynamics models to assess the validity of such extrapolations, and defines the variables needed to compare the results from molecular dynamics and suction experiments. The encouraging agreement contributed to the confidence in the proposed procedure, which enabled a new strategy that uses molecular dynamics data to model the macroscopic behaviour of compacted sodium bentonites.

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Section: Mo Mnccmentioning

confidence: 99%

Molecular dynamics data for modelling the microstructural behaviour of compacted sodium bentonites

Navarro

Yustres

Jenni

et al. 2021

Applied Clay Science

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“…The microstructural level is characterized by the predominance of thermodynamic, chemical and electrical effects caused by the proximity of the clay particles (with negative net electrical charge). In the present work, it is assumed that at the microstructural functional level a) water is adsorbed and does not flow under conventional hydrodynamic gradients and b) electrostatic effects mainly occur at this level, presenting an average electrical potential different from the one present at the macrostructural functional level [47,48].…”

Section: Mathematical Formulationmentioning

confidence: 99%

Donnan-ion hydration model to estimate the electroosmotic permeability of clays

Yustres

López-Vizcaíno

Cabrera

et al. 2020

Electrochimica Acta

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Electroosmotic permeability is a soil parameter that is fundamental for designing and implementing environmental remediation, dewatering, or soil stabilization processes. It presents a narrow range of variation compared to hydraulic permeability, so that on many occasions no experimental tests are carried out to determine it. Traditionally, the Helmholtz-Smoluchowski equation has been used to estimate electroosmotic permeability, despite having several drawbacks that make it difficult to apply, as it was deduced for large capillaries (unusual in clays) and its dependence on the potential zeta of the soil, difficult to measure and dependent on a variety of factors that are difficult to control. The present work describes a semi-empirical formulation that allows the estimation of the electroosmotic permeability as a function of the specific surface area and the total void ratio and is based on the Donnan equilibrium and the ion hydration models. The parameters for modelling are calibrated and validated with experimental data, obtaining better results than those given by the Helmholtz-Smoluchowski model. In addition, the expected trends in the behavior of clays that can be found in the literature are obtained in a quantitative and consistent manner for different types of clays with variable water content and pore water salinity. KEYWORDSÁnge 3 / 36 Ji m in 10 -5 (mol s -1 m -2 ) ue,i m in 10 -10 (m 2 V -1 s -1 ) ci m in 10 -5 (mol kgw -1 ) Ji m in 10 -9 (mol s -1 m -2 ) Exper * . Model K-C Exper Model K-C

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“…where ρ m is the microstructural water density, p is the net mean stress, Δs mNCC that defines the increase in microstructural suction due to the contribution to the chemical potential by the ions in excess of the CEC (defined in [18]) and s mS is the "structural" suction of the microstructure and it is defined by a state function ( Figure 1) characterised by microstructural void ratio [19]. Adopting equilibrium between structural levels, the chemical potentials are equal in macrostructural, Eq.…”

Section: Conceptual Modelmentioning

confidence: 99%

“…The activity coefficients in macrostructural water have been estimated using the LLNL (Lawrence Livermore National Laboratory) model for charged species [31] and Drummond approach for uncharged species [32]. The chemical composition in microstructural water is calculated assuming Donnan equilibrium between both structural levels [18]. The activity coefficients in microstructural water were assumed equal to the macrostructural one.…”

Section: Conceptual Modelmentioning

confidence: 99%

Development of a THMC code for bentonites in COMSOL Multiphysics

et al. 2020

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The proposed use of active clays for the isolation of radioactive wastes in deep geological repositories has been followed by a deeper understanding of this type of soils. This increased knowledge has led to the need for both conceptual and numerical models capable of capturing the main trends in behaviour and the different couplings between different physical-chemical phenomena. In addition, the model must have a high degree of flexibility that enables it to accommodate future developments or new relevant phenomena. This work presents a numerical THMC code developed entirely on the COMSOL Multiphysics numerical implementation platform, which provides the required adaptability. This model includes, for the first time in this environment, a reactive transport model in unsaturated porous media for a relevant geochemical system (consistent with the MX-80 bentonite) together with a THM model based on a double porosity approach. The chemical potentials of water and solutes are used for the definition of thermodynamic equilibria between both porosity levels. Trends in the behaviour of a bentonite sample under oedometric conditions are satisfactorily simulated in response to a process of saturation and change in salinity conditions. Variations in swelling pressure, porosity distribution or dissolution/precipitation of the main accessory minerals are analysed and explained by means of the proposed conceptual model.

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Predicting the swelling pressure of MX-80 bentonite

Cited by 30 publications

References 31 publications

Molecular dynamics data for modelling the microstructural behaviour of compacted sodium bentonites

Molecular dynamics data for modelling the microstructural behaviour of compacted sodium bentonites

Donnan-ion hydration model to estimate the electroosmotic permeability of clays

Development of a THMC code for bentonites in COMSOL Multiphysics

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