Laboratory results from hydro-mechanical tests on a water unsaturated bentonite

Dueck, Ann

doi:10.1016/j.enggeo.2007.11.001

Cited by 27 publications

(16 citation statements)

References 3 publications

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“…This forms a state surface between suction, degree of saturation, and stress (Gallipoli et al 2003;Dueck 2004;Dueck and Börgesson 2007). The free swell water retention experimental data provide the maximum water content at zero confining stress over the full range of applied suctions and associated changes in void ratio.…”

Section: The Hydraulic Processmentioning

confidence: 99%

“…Wetting-induced collapse is modelled through an applied load activated when a threshold defined in terms of axial stress and net suction is exceeded. Water retention behaviour in unsaturated expansive soils has been shown to be both stress and volume dependent (Gallipoli et al 2003;Dueck 2004;Dueck and Börgesson 2007). A simple extension to the method proposed by Dueck and Börgesson (2007) has been implemented in this model to complete the hydro-mechanical coupling.…”

Section: Introductionmentioning

confidence: 99%

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A nonlinear elastic approach to modelling the hydro-mechanical behaviour of the SEALEX experiments on compacted MX-80 bentonite

et al. 2016

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Hydraulic seals using compacted sand-bentonite blocks are an important part of the closure phase of deep geological disposal facilities for the isolation of many categories of radioactive wastes. An understanding of the hydromechanical behaviour of these seals and the ability to model their behaviour is a key contribution to safety cases and licence applications. This work reports the development of a hydro-mechanically coupled model and its application to the simulation of a range of test conditions investigated in the SEALEX experiments conducted by IRSN at Tournemire URL. The work has been conducted as part of the recently completed DECOVALEX-2015 project. Richards' equation for unsaturated fluid flow is coupled to a nonlinear elastic strain-dependent mechanical model that incorporates a moving finite element mesh, and calibrated against laboratory experiments. Stress and volumetric dependencies of the water retention behaviour are incorporated through the Dueck suction concept extended to take into account permanent changes in water retention behaviour during consolidation. Plastic collapse in laboratory results is modelled with the application of a source term activated by a threshold defined in terms of the net axial stress and net suction. The model is used to simulate both a 1/10 scale mock-up laboratory test and full-scale in situ performance test and is capable of reproducing the major trends in the data with just nine mechanical parameters and an experimentally defined stress threshold.

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Section: The Hydraulic Processmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A nonlinear elastic approach to modelling the hydro-mechanical behaviour of the SEALEX experiments on compacted MX-80 bentonite

et al. 2016

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“…In most cases, the materials are either pure bentonite (to cite but a few of them: Marcial et al 2002, Lloret et al 2003, Dueck 2008, Ye et al 2009, Tang & Cui 2010 or mixtures of bentonite with sand (see for instance Yong et al 2003, Blatz et al 2002, Sun et al 2010, Agus et al 2012, Wang et al 2013 or with excavation products (Borgesson et al 2003, Mata & Ledesma 2003, Wang et al 2012). The sealing material may also take different forms, namely compacted blocks or mixture of powder and pellets, and have different ranges of dry density.…”

Section: Introductionmentioning

confidence: 98%

Hydration kinetics of compacted low-density bentonite

Dieudonné¹,

Charlier²,

Romero³

2014

Unsaturated Soils: Research &Amp; Applications

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The hydration kinetics of a compacted low-density bentonite is investigated from both experimental and numerical points of view. A water retention curve and water permeability under saturated conditions were determined to characterize the hydraulic behaviour of the compacted material. The evolution of swelling strains developed during a soaking test performed under oedometer conditions is interpreted as a measure of the hydration kinetics. While soaking was immediate, the vertical strains appeared to develop very slowly during the first two hours of testing. Numerical simulations of the soaking test were performed to achieve a better understanding of the hydration mechanisms. It is shown that the numerical results overestimate the hydration rate of the sample. Two explanations for the very slow hydration are proposed and discussed in the paper, namely the formation of clay gel and an initial drying of the sample.In all concepts of disposal, the engineered barrier will be initially unsaturated and will be subjected to hydration from the surrounding saturated host rock. During this process, it will tend to expand and will develop swelling stresses, hence modifying the structure and the water transfer properties of the material. Although transient, this stage is very important as it is believed to directly impact the final state and effectiveness of the system. A good understanding of the hydration mechanisms is thus essential to assess the performance of the engineered barriers and the time needed for their full saturation.Given the very low permeability of the material and the complex phenomena involved in the problem, it has proved useful to perform elementary laboratory experiments on small samples. These tests generally provide useful qualitative and quantitative information along a given stress path. This information should be complemented with numer-

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“…To date, few experimental studies have investigated both volumetric and water retention behaviours of compacted bentonite with the aim of obtaining suction -degree of saturation relationships (Delage et al 1998;Dueck 2008;Ajdari et al 2013). In this paper, the water retention properties of a compacted bentonite/sand mixture are investigated along wetting paths, under both constant volume and free swelling conditions.…”

Section: Introductionmentioning

confidence: 99%

Competing effects of volume change and water uptake on the water retention behaviour of a compacted MX-80 bentonite/sand mixture

Gatabin

Talandier

Collin

et al. 2016

Applied Clay Science

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Bentonite-based materials have been studied as potential barriers for the geological disposal of radioactive waste. In this context, the hydro-mechanical behaviour of the engineered barrier is first characterized by free swelling conditions (as a consequence of the progressive filling of technological gaps) followed by constant volume conditions. This paper presents an experimental study conducted in order to characterize the water retention behaviour of a compacted MX-80 bentonite/sand mixture. The water retention properties upon wetting were investigated under both free swelling and constant volume conditions. In the high suction range, the water content was not influenced by the imposed volume constraints. On the contrary, swelling significantly affected the water retention behaviour at low suctions, and the quantity of water stored was higher under free swelling conditions than it was under prevented swelling. In this case, competing effects between bentonite swelling and water uptake did not lead to an increase of the degree of saturation upon wetting, as it was observed for samples wetted under constant volume conditions. The influence of the very strong hydro-mechanical coupling is further discussed.

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Laboratory results from hydro-mechanical tests on a water unsaturated bentonite

Cited by 27 publications

References 3 publications

A nonlinear elastic approach to modelling the hydro-mechanical behaviour of the SEALEX experiments on compacted MX-80 bentonite

A nonlinear elastic approach to modelling the hydro-mechanical behaviour of the SEALEX experiments on compacted MX-80 bentonite

Hydration kinetics of compacted low-density bentonite

Competing effects of volume change and water uptake on the water retention behaviour of a compacted MX-80 bentonite/sand mixture

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