Geohydromechanical processes in the Excavation Damaged Zone in crystalline rock, rock salt, and indurated and plastic clays—in the context of radioactive waste disposal

Tsang, Chin‐Fu; Bernier, Frédéric; Davies, Christophe

doi:10.1016/j.ijrmms.2004.08.003

Cited by 385 publications

(184 citation statements)

References 18 publications

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“…Thus, it seems that not only the composition of cementitious composites and cementitious materials and its spatial distribution but also the surrounding environment affect sealing behavior. Furthermore, fracture sealing has also been observed in various rocks (e.g., Fisher and Brantley 1992;Gratier et al 1994;Evans and Chester 1995;Tsang et al 2005).…”

Section: Introductionmentioning

confidence: 97%

Observation of fracture sealing in high-strength and ultra-low-permeability concrete by micro-focus X-ray CT and SEM/EDX

et al. 2014

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Fracture sealing by precipitation is known to occur in high-strength and ultra-lowpermeability concrete (HSULPC) immersed in water. Because a high ability to retard radionuclide migration is required for HSULPC, understanding both the sealing process and the composition of sealing deposits is important to identify optimum conditions for significant sealing. In this study, sealing of a macro-fractured HSULPC specimen with initial aperture of approximately 0.1 mm was investigated in simulated seawater over 49 days. The composition of sealing deposits at 49 days after immersion was clarified by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDX), and the progress of sealing during the 49 days was clarified by image analysis with micro-focus X-ray computed tomography (X-rayCT). Both the SEM/EDX and X-rayCT results showed that significant sealing was attained only near the outermost part of the specimen. The SEM/EDX results showed that a thin brucite layer formed on the entire specimen surface over which significant precipitation of calcium carbonate occurred and sealed the macro-fracture only near the outermost part of the specimen. The X-rayCT results indicated that the amount of sealing deposits in the macro-fracture (P seal ) reached 70 % in the mostly sealed region at 49 days and the rate of change in P seal became maximum (3.7 % day -1 ) during 7-21 days after immersion, then decreased. In conclusion, Revised_Manuscript Click here to download Manuscript: IJF_manuscript_FRAC_Rev1.doc Click here to view linked References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 the findings in this study represent an important clue in the search for optimum conditions to achieve fracture sealing in HSUPLC.

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Section: Introductionmentioning

confidence: 97%

Observation of fracture sealing in high-strength and ultra-low-permeability concrete by micro-focus X-ray CT and SEM/EDX

et al. 2014

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“…Environmental impact zones around the underground facility are classified into an Excavation Damaged Zone (EDZ) near the tunnel and an Excavation disturbed Zone (EdZ) comprising the EDZ and areas around the excavations (Olsson and Winberg 1996;Bossart et al 2002;Tsang et al 2005). In an EDZ, mechanical and hydrogeological properties of the rock were intensely fractured during excavation, and the chemical properties were also modified by shotcrete, grouting, and air circulation.…”

Section: Resultsmentioning

confidence: 99%

Hydrochemical disturbances measured in groundwater during the construction and operation of a large-scale underground facility in deep crystalline rock in Japan

et al. 2015

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Changes in the hydrochemical conditions of groundwater were evaluated following the construction of a large-scale underground facility at the Mizunami Underground Research Laboratory (MIU), Japan. The facility was constructed to a depth of 500 m in sedimentary and granitic rocks. Drawdown of the groundwater level in the range of several tens to hundreds of meters was observed up to hundreds of meters away from the shafts during the first ten years of facility construction and operation. Subsequent changes in groundwater chemistry occurred due to upconing of high-salinity groundwater from the deepest part of the shaft and the infiltration of low-salinity shallow groundwater. We predict that future deep groundwater chemistry in the vicinity of the MIU facility will resemble that of the present-day shallow groundwater. Multivariate statistical analysis provides fundamental insights into such a site. We found that the extent of hydrochemical variability related to MIU construction and operation was dependent on the distance from the facility shafts and galleries and on hydrogeological compartmentalization resulting from lithological boundaries (such as permeable conglomerates vs. more compact lithological units) and other features (such as faults or clay layers). We conclude that hydrochemical impact assessment of groundwater in low-permeability rock is essential prior to the construction of such a facility. This should include characterization of hydrogeological structures and compartments to propose suitable location of shafts and galleries.

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“…Among the existing enhanced models with regularisation methods that allow a proper modelling of the strain localisation behaviour, we use the coupled local second gradient model under unsaturated conditions. Moreover, it is known that hydraulic permeability is not homogeneous in the damaged zone (Tsang et al 2005), then its modification is considered through a dependency with shear band properties.…”

Section: Introductionmentioning

confidence: 99%

Using Shear Strain Localisation to Model the Fracturing Around Gallery in Unsaturated Callovo-Oxfordian Claystone

Pardoen

Levasseur

Collin

2014

Springer Series in Geomechanics and Geoengineering

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Galleries drilling leads to damage propagation, fracturing and properties modifications in the surrounding medium. The prediction of the damaged zone behaviour is an important matter and needs to be properly assessed. To do so the fractures can be modelled using shear strain localisation. The coupled local second gradient model is used under unsaturated conditions to correctly model the strain localisation behaviour. The permeability evolution and the rock desaturation due to air ventilation in galleries are considered. Finally, a hydro-mechanical modelling of a gallery excavation in Callovo-Oxfordian claystone is performed leading to a fairly good representation of the damaged zone.

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Geohydromechanical processes in the Excavation Damaged Zone in crystalline rock, rock salt, and indurated and plastic clays—in the context of radioactive waste disposal

Cited by 385 publications

References 18 publications

Observation of fracture sealing in high-strength and ultra-low-permeability concrete by micro-focus X-ray CT and SEM/EDX

Observation of fracture sealing in high-strength and ultra-low-permeability concrete by micro-focus X-ray CT and SEM/EDX

Hydrochemical disturbances measured in groundwater during the construction and operation of a large-scale underground facility in deep crystalline rock in Japan

Using Shear Strain Localisation to Model the Fracturing Around Gallery in Unsaturated Callovo-Oxfordian Claystone

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