Inputs from in situ experiments to the understanding of the unsaturated behaviour of Callovo-Oxfordian claystone

Armand, Gilles; Djizanne, Hippolyte; Zghondi, Jad; Vaissière, Rémi de La; Talandier, Jean; Conil, Nathalie

doi:10.1051/e3sconf/20160903004

Cited by 8 publications

(5 citation statements)

References 23 publications

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“…In the present analysis, however, the simulation of the unsaturated zone in the COx claystone is not a major objective and, therefore, the zero liquid pressure boundary condition is considered appropriate. In addition, ventilation experiments at the Mont Terri (Mayor et al, 2007) and MHM (Armand et al, 2016) URLs revealed that the effect of dry air circulation is very limited, and the unsaturated zone extends only a very short length into the claystone.…”

Section: Main Features Of the Finite Element Modelmentioning

confidence: 99%

Numerical simulation of underground excavations in an indurated clay using non-local regularisation. Part 1: formulation and base case

et al. 2022

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The paper presents the numerical simulation of an underground excavation in the Callovo-Oxfordian argillaceous formation, performed in the Meuse/Haute-Marne underground research laboratory, within the context of deep geological nuclear waste disposal. The constitutive model adopted incorporates a number of characteristic features of the hydromechanical behaviour of the Callovo-Oxfordian claystone, and other indurated clays, including anisotropy and time-dependent deformations. Model parameters have been largely determined from available experimental results. Particular attention has been given to the incorporation of a nonlocal formulation in order to simulate localised deformations objectively. It is shown that the numerical analysis is able to provide a very satisfactory reproduction of the extent and configuration of the excavation-induced fractured zone, the development of rock displacements, and the evolution of water pressures in the rock. The analysis is also able to provide a deeper insight into the mechanisms underlying the generation of water pressures inside the rock mass.

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Section: Main Features Of the Finite Element Modelmentioning

confidence: 99%

Numerical simulation of underground excavations in an indurated clay using non-local regularisation. Part 1: formulation and base case

et al. 2022

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“…Under natural conditions, potential clay host rocks as well as active clay liners or clay backfills are generally water saturated. During the construction of an underground repository, however, the contact with the unsaturated atmosphere leads to a partial desaturation of the rocks (e.g., Gimmi et al, 1997;Armand et al, 2016). Also, the bentonite backfill will be emplaced in a dry state, which may lead to a partial desaturation of the surrounding rock (e.g., Gens et al, 2002;Dessirier et al, 2016).…”

Section: Influence Of Partial Saturationmentioning

confidence: 99%

Water retention and diffusion in unsaturated clays: Connecting atomistic and pore scale simulations

Gimmi

Churakov

2019

Applied Clay Science

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Molecular diffusion is the dominant solute transport process in clays and claystones that are considered as sealing materials in the deep geological disposal of radioactive waste. These materials are typically water saturated, but during construction and later, at elevated temperatures or when gas may be produced, unsaturated conditions prevail. Investigating the clay's water retention properties as well as solute transport under unsaturated conditions is therefore mandatory. Here, functional dependencies of these properties were derived from atomistic and pore-scale simulations. In the absence of tomographic maps that resolve all pores in clays, model clay structure maps with different pore size distributions were generated using a previously developed algorithm. Upscaled water retention functions and upscaled diffusion coefficients of unsaturated samples were derived from these maps based on the shifted Young-Laplace equation that considers film adsorption and capillary condensation. Pore-scale parameters (diffusion coefficients, water film thickness) used for the upscaling were taken from molecular dynamics (MD) simulations, thus connecting MD and pore-scale simulations. We focused on effects of the pore size distribution and of the adsorbed water film on upscaled parameters. Samplescale diffusion coefficients were clearly reduced in unsaturated samples compared to the saturated state, with less reduction when including adsorbed water films. The reduction was stronger in samples with a narrow size distribution of the interparticle pores as compared to those with a wide distribution (but equal mean size). The results follow the trends of the experimental data, even though the scale of the simulations is still clearly smaller than that of typical experiments.

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“…Armand et al [3] reported that the convergence of the drifts was affected by the pattern and the density of fractures in EDZ. Moreover, unsaturation in COx claystone was also induced by the ventilation in URL [4]. In this case, it is important to well understand the hydro-mechanical behaviour of damaged COx claystone for estimating the safety performance of potential repository.…”

Section: Introductionmentioning

confidence: 99%

Investigation into the compression behaviour of unsaturated damaged Callovo-Oxfordian claystone

Wang

Cui

et al. 2023

E3S Web of Conf.

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In this study, the compression behaviour of unsaturated damaged COx claystone is investigated by performing high pressure oedometer tests with controlled suction. The damaged oedometer samples were prepared by shearing the claystone in triaxial conditions. Four high pressure oedometer tests were conducted using different controlled suctions. The effects of suction and damage on the swelling and compression were investigated in oedometer. Results show that the intact claystone exhibits a larger swelling strain than that of the damaged one at the same imposed suction. The damaged claystone at a lower suction displays a smaller yield stress and higher compressibility, and exhibits a larger compression index Cc than the intact one, evidencing the effect of damage. In addition, the step compression index Cc* increases with the increase of vertical stress, while deceases with the decrease of suction. This indicates the dependencies of compression behaviour on vertical stress and suction.

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Inputs from in situ experiments to the understanding of the unsaturated behaviour of Callovo-Oxfordian claystone

Cited by 8 publications

References 23 publications

Numerical simulation of underground excavations in an indurated clay using non-local regularisation. Part 1: formulation and base case

Numerical simulation of underground excavations in an indurated clay using non-local regularisation. Part 1: formulation and base case

Water retention and diffusion in unsaturated clays: Connecting atomistic and pore scale simulations

Investigation into the compression behaviour of unsaturated damaged Callovo-Oxfordian claystone

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