Investigating the swelling pressure of compacted crushed-Callovo-Oxfordian claystone

Tang, Chaosheng; Tang, Anh-Minh; Cui, Yu‐Jun; Delage, Pierre; Schroeder, Christian; Laure, Emmanuel De

doi:10.1016/j.pce.2011.10.001

Cited by 43 publications

(21 citation statements)

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“…The mixtures were considered for use in the construction of seals in disposal boreholes, drifts and shafts. The COx powder has grain sizes similar to those studied by others (Tang et al 2011). The delivered MX80 bentonite was relatively dry with a water content of w ¼ 9.6%.…”

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confidence: 64%

Characterization of excavated claystone and claystone–bentonite mixtures as backfill/seal material

Zhang

2014

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Crushed claystone produced by excavation of repository openings has been investigated as backfill/seal material. The raw coarse-grained claystone can be used for backfilling repository openings and, in mixture with bentonite, for sealing boreholes, drifts and shafts. The investigation programme focused on characterizing the thermo-hydro-mechanical properties of the excavated Callovo-Oxfordian claystone and the compacted claystone-bentonite mixtures, including (1) mechanical compaction, (2) gas and water permeability as a function of porosity, (3) water retention and saturation, (4) swelling capacity and (5) thermal properties of the materials. The major results are presented in this paper.The disposal concepts developed by many countries for repositories in clay formations are based on the principle of a multi-barrier system, which comprises the natural geological barriers provided by the host rock and its surroundings, and an engineered barrier system (EBS). After emplacement of radioactive waste containers, the disposal boreholes, drifts and shafts must be backfilled and sealed with suitable materials to prevent a release of radionuclides into the biosphere. The geotechnical properties of each EBS component must be specified with regard to their functional requirements. In most concepts, bentonite-based materials are considered for use in filling and sealing disposal boreholes. For instance, the Swiss concept (Nagra 2002) provides for waste containers being emplaced on compacted bentonite blocks positioned on the drift floor and the remaining space being backfilled with granular bentonite. Meanwhile, according to the French concept (Andra 2005), the drifts are backfilled with excavated claystone and sealed with compacted bentonite-based seal core confined between concrete plugs.Crushed claystone produced by the excavation of repository openings may be a favourable alternative as backfill/seal material; its use has many advantages, including chemical-mineralogical compatibility with the host rock, availability in sufficient amounts, low cost of material preparation and transport, and there is no need for it to occupy surface space if it is used as backfill for the excavated claystone. Indeed, crushed claystone with coarse grains can be considered for use for backfilling repository openings and, in mixture with bentonite, for sealing boreholes, drifts and shafts. Recently, a research programme has been conducted at the GRS geotechnical laboratory to characterize the geotechnical properties of the excavated Callovo-Oxfordian claystone and the compacted claystone -bentonite mixtures under relevant repository conditions. The following properties of the backfill/seal materials are most important in terms of their barrier functions and have thus been investigated:(1) The compaction behaviour of the backfill material in underground openings. This controls mechanical interactions with support linings (if existing) and with the surrounding rock and, in turn, determines the evolution of backfill porosity and permeability....

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confidence: 64%

Characterization of excavated claystone and claystone–bentonite mixtures as backfill/seal material

Zhang

2014

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“…In the case of MMA the intercalated layers are always limited to two, leading to basal spacing mimicking 2-3 water layers. Like vapour water hydration (Tang et al, 2011), the intercalation of two MMA molecule layers into the interlayer spacing ( Figure 2b) leads to swelling of particles filling up the inter-particle porosity with limited closure of inter-aggregate porosity. Such swelling development without the momentary decrease of swelling pressure over time has been also observed under RH regimes when particle swells without total interaggregate porosity filling (Likos and Wayllace, 2010;Tang et al, 2011).…”

Section: Explanation Of Peak Occurrencementioning

confidence: 99%

“…Like vapour water hydration (Tang et al, 2011), the intercalation of two MMA molecule layers into the interlayer spacing ( Figure 2b) leads to swelling of particles filling up the inter-particle porosity with limited closure of inter-aggregate porosity. Such swelling development without the momentary decrease of swelling pressure over time has been also observed under RH regimes when particle swells without total interaggregate porosity filling (Likos and Wayllace, 2010;Tang et al, 2011). Instead of microstructure reorganisation in between the aggregates, the intercalation of water layers inside and between particles leads to their swelling, which fills up the inter-aggregate pores.…”

Section: Explanation Of Peak Occurrencementioning

confidence: 99%

“…They used various investigative techniques (XRD, SAXS/SANS, FIB/SEM, MIP), and from those results, we can schematically consider the total porosity to be composed of pores of different sizes (Figure 1) such as the interlayer space, the porosity between particles (inter-particle porosity) and the porosity between aggregates (inter-aggregate porosity). The effect of hydration on microstructure has been described (Delage et al, 2006;Devineau et al, 2006;Tang et al, 2011;Van Geet et al, 2005) but often only considering one or two porosity levels, e.g. inter-aggregate and/or interlayer porosity.…”

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Swelling pressure development and inter-aggregate porosity evolution upon hydration of a compacted swelling clay

Massat

Cuisinier

Bihannic

et al. 2016

Applied Clay Science

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A specific oedometer cell has been set up to measure the swelling pressure of compacted montmorillonites at constant volume and to concomitantly visualize the evolution, upon wetting, of how the microstructure is organised through X-ray microtomography. The swelling pressure experiments were conducted with solvents of various natures. In addition to conventionally used water and saline solutions, we used an organic solvent (methyl methacrylate-MMA). We chose this to explore the effect of its different physical and chemical properties, and to differentiate the respective roles of crystalline and osmotic pressures on macroscopic swelling behaviour. The results, which combined both swelling pressure measurements and quantification of microstructure evolution upon hydration for the two different solutes, give sound understanding on the development of osmotic and/or crystalline swelling and their relative impact both on the microstructure and on the magnitude of the macroscopic swelling pressure of compacted montmorillonites.

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“…We utilized an isochoric cell which measures total stress under constant volume conditions (developed by Tang et al (2011) and adapted in this study to resist pressurized CO 2 ). From bottom to top (Fig.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Adsorptive-mechanical properties of reconstituted granular coal: Experimental characterization and poromechanical modeling

Espinoza

Vandamme

Dangla

et al. 2016

International Journal of Coal Geology

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Investigating the swelling pressure of compacted crushed-Callovo-Oxfordian claystone

Cited by 43 publications

References 45 publications

Characterization of excavated claystone and claystone–bentonite mixtures as backfill/seal material

Characterization of excavated claystone and claystone–bentonite mixtures as backfill/seal material

Swelling pressure development and inter-aggregate porosity evolution upon hydration of a compacted swelling clay

Adsorptive-mechanical properties of reconstituted granular coal: Experimental characterization and poromechanical modeling

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