Numerical study of the chemo-mechanical behavior of FEBEX bentonite in nuclear waste disposal based on the Barcelona expansive model

Xu, Hao; Zheng, Liange; Rutqvist, Jonny; Birkhölzer, Jens

doi:10.1016/j.compgeo.2020.103968

Cited by 17 publications

(4 citation statements)

References 61 publications

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“…Deuteric weathering affected the pyroclastic materials and the perlites in aqueous media with an alkaline pH, with high Mg and Ca concentrations, but lacking K [15]. From a mineralogical point of view, the chemical transformations occur mainly as formation of clay minerals, montmorillonite being the prevailing one accompanied by cristobalite [33].…”

Section: Summary Discussionmentioning

confidence: 99%

“…This study of the Oraşu Nou bentonite reveals a good quality raw material that can be used in many fields of activity: agriculture [22] to immobilize fungicides or insecticides [25], inactivate heavy metals in polluted soils, especially zinc [28], nuclear waste storages [32,33].…”

Section: Summary Discussionmentioning

confidence: 99%

“…Bentonites mixed with zeolites have been used to inactivate heavy metals in polluted soils, especially zinc [28]. They can also be used in pollutant removal processes for industrial or civilian residual waters [29,30], for the purification of industrial gases, protection of waste storage areas [31], including nuclear waste storages [32,33]. Bentonites from the Oraşul Nou deposit can be considered a potential buffer material for isolation of radioactive waste, where they can be used due to their low permeability and high CEC [34].…”

Section: Introductionmentioning

confidence: 99%

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Mineralogical and Physico-Chemical Characterization of the Oraşu-Nou (Romania) Bentonite Resources

Damian

Szakács

et al. 2021

Minerals

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The objective of this study is to describe the mineralogical composition and chemical properties of the Oraşu Nou bentonite, from northwestern Romania. For mineralogical determinations, the following were used: X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FR-IR), thermogravimetric analysis, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX). The chemical compositions and physical properties of the bentonites and bentonitized rocks were also determined. Calcium type montmorillonite is the predominant mineral in this deposit. Its average mass fraction is between 35% and 75%, reaching up to 95%. A small amount of halloysite and very fine cristobalite were also identified in the fine fraction. Quartz, feldspar, and kaolinite were identified as impurities. The average pH of natural bentonite is 6.2. Its cation exchange capacity (CEC) is in the lower-middle range for smectites at 45.89 cmol/kg, absorption capacity 43.58 mL/g, swelling degree 9.41%. Because of the high amounts and purity of montmorillonite, the valuable component mineral, the way is open to an easy refinement of this important resource. This way very high-quality colloidal suspensions can be obtained which can be used in the most modern applications of micro- and nanostructured materials.

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Section: Summary Discussionmentioning

confidence: 99%

Section: Summary Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mineralogical and Physico-Chemical Characterization of the Oraşu-Nou (Romania) Bentonite Resources

Damian

Szakács

et al. 2021

Minerals

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“…Montmorillonite (MMT) consists of well-defined layers separated by interlayer spaces and has great water absorption potential [1][2][3][4]. Thus, it is often used as clay barriers or adsorption material in environmental geotechnical engineering, for example, the backfill in the nuclear waste disposal and the cushion in the landfill [5][6][7][8][9][10]. It is very challenging to directly measure the fundamental mechanical properties of MMT [11,12].…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation of Nanoscale Elastic Properties of Hydrated Na-, Cs-, and Ca-Montmorillonite

et al. 2022

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The knowledge of nanoscale mechanical properties of montmorillonite (MMT) with various compensation cations upon hydration is essential for many environmental engineering-related applications. This paper uses a Molecular Dynamics (MD) method to simulate nanoscale elastic properties of hydrated Na-, Cs-, and Ca-MMT with unconstrained system atoms. The variation of basal spacing of MMT shows step characteristics in the initial crystalline swelling stage followed by an approximately linear change in the subsequent osmotic swelling stage as the increasing of interlayer water content. The water content of MMT in the thermodynamic stable-state conditions during hydration is determined by comparing the immersion energy and hydration energy. Under this stable hydration state, the nanoscale elastic properties are further simulated by the constant strain method. Since the non-bonding strength between MMT lamellae is much lower than the boning strength within the mineral structure, the in-plane and out-of-plane strength of MMT has strong anisotropy. Simulated results including the stiffness tensor and linear elastic constants based on the assumption of orthotropic symmetry are all in good agreement with results from the literature. Furthermore, the out-of-plane stiffness tensor components of C33, C44, and C55 all fluctuate with the increase of interlayer water content, which is related to the formation of interlayer H-bonds and atom-free volume ratio. The in-plane stiffness tensor components C11, C22, and C12 decrease nonlinearly with the increase of water content, and these components are mainly controlled by the bonding strength of mineral atoms and the geometry of the hydrated MMT system. Young’s modulus in all three directions exhibits a nonlinear decrease with increasing water content.

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Investigation on the Instability Mechanism of Expansive Soil Slope With Weak Interlayer Based on Strain Softening

Xu,

Jiang,

et al. 2024

Num Anal Meth Geomechanics

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Expansive soils are widespread in the world and coincide with areas of high human activity. The main cause of deep instability of expansive soil slopes is due to their softening caused by excavation and seepage. By developing a comprehensive numerical model based on the theory of unsaturated soil, this study examines the characteristics of stress and displacement distribution of expansive soil slopes through hydraulic‐mechanical coupled numerical simulation. This study analyzes the evolution patterns of slopes with excavation unloading and seepage of water storage to reveal the mechanisms of deep‐seated instability of expansive soil slopes. The findings demonstrate that: The instability of expansive soil slopes begins at the foot of the slope and propagates along the interlayer, affecting the entire slope. Excavation leads to the softening of the expansive soil interlayer and the transfer of shear stress. During water storage, the weakening of the soil strength results in slope instability along the weak interlayer slip. Softening of the expansive soil interlayer facilitates the redistribution of shear forces in the slope and alters the distribution law of the plastic zone in the deep layer. Overly slowing down the slope leads to significant excavation unloading, which is detrimental to the slope's stability.

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Numerical study of the chemo-mechanical behavior of FEBEX bentonite in nuclear waste disposal based on the Barcelona expansive model

Cited by 17 publications

References 61 publications

Mineralogical and Physico-Chemical Characterization of the Oraşu-Nou (Romania) Bentonite Resources

Mineralogical and Physico-Chemical Characterization of the Oraşu-Nou (Romania) Bentonite Resources

Molecular Dynamics Simulation of Nanoscale Elastic Properties of Hydrated Na-, Cs-, and Ca-Montmorillonite

Investigation on the Instability Mechanism of Expansive Soil Slope With Weak Interlayer Based on Strain Softening

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