Determination of the porosity, permeability and diffusivity of rock in the excavation-disturbed zone around full-scale deposition holes using the -PMMA and He-gas methods

Autio, Jorma; Siitari-Kauppi, Marja; Timonen, J.; Hartikainen, K.; Hartikainen, Juha

doi:10.1016/s0169-7722(98)00112-0

Cited by 24 publications

(7 citation statements)

References 1 publication

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“…The sample holder has been designed for the specific surface area determination of large rock samples. A large rock sample was used because sawing or drilling can produce a disturbed zone penetrating millimeters to centimeters into the sample [7]. The ratio of disturbed rock volume to total sample rock volume becomes smaller with increasing rock sample size, thus a large piece is preferred.…”

Section: Bet-determinationsmentioning

confidence: 99%

Measuring sorption coefficients and BET surface areas on intact drillcore and crushed granite samples

André¹,

Neretnieks

Malmström

2008

Radiochimica Acta

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In general sorption coefficients, K d , cat ion exchange capacity, CEC, and BET surface areas are measured on crushed rock samples because it is very time consuming to measure K d and CEC on larger rock pieces as it takes a long time for the sorbing species to penetrate into and equilibrate a large sample. Also conventional sample holders for BET measurements are too small to hold a large sample.We have manufactured large sample holders for BET measurements and modified the equipment so that it is possible to measure BET surface areas on samples with 50 mm diameter and up to 100 mm length. Results are presented for intact pieces and compared to results on crushed material from the same drillcore.For K d and CEC measurements we have developed a technique and equipment by which ions can be made to rapidly intrude into and equilibrate the internal surfaces of the same size samples as mentioned above. The method is based on electro-migration where the sample is placed between two vessels one with an anode and other with a cathode. The electric potential gradient drives the ions into and through the sample very much faster than molecular diffusion does. With Cs as the sorbing ion a few weeks were sufficient to equilibrate the 50 mm long sample. In previous diffusion experiments it took more than a year to equilibrate a 15 mm thick sample. A special mixing technique eliminates the development of low and high pH in the electrode compartments.K d results from measurements on an intact drillcore are presented and comparison is made with results obtained on crushed material from the same bore core. The results from the sorption experiments are compared with the results from the BET surface area determinations in an attempt to evaluate the use of the BET surface area as a proxy for sorption behaviour.

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Section: Bet-determinationsmentioning

confidence: 99%

Measuring sorption coefficients and BET surface areas on intact drillcore and crushed granite samples

André¹,

Neretnieks

Malmström

2008

Radiochimica Acta

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“…The extent of EDZ can be identified by the changes in matrix geophysical and hydromechanical properties that are determined by the tests on borehole cores. For instance, Matray et al (2007) determined the EDZ extent in Tournemire's argillite (France) through changes in degree of saturation; Autio et al (1998) did that in Äspö Hard Rock (Sweden) through changes in porosity.…”

Section: Introductionmentioning

confidence: 99%

Impact of excavation damage on the thermo-hydro-mechanical properties of natural Boom Clay

Dao

Cui

Tang

et al. 2015

Engineering Geology

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International audienceBoom Clay has been considered as a potential host-rock for the geological radioactive waste disposal in Belgium. In this context, it is important to well understand the thermo-hydro-mechanical behaviour of this clay around the disposal galleries. In this study, the effect of excavation damage on the thermo-hydro-mechanical properties of natural Boom Clay around the Connecting gallery (excavated in 2002) in the Mol underground Research Laboratory HADES (High-Activity Disposal Experimental Site) was investigated. Several samples taken from a horizontal borehole drilled in July 2012 were tested. The thermal conductivity in three different orientations (perpendicular, parallel, and 45° to the bedding plane) was measured using the needle probe method. The results show a cross-anisotropy of natural Boom Clay and an impact of the excavation damage on the thermal property of samples near the gallery. To further investigate the anisotropy behaviour, bender element tests were carried out under unconfined conditions to determine the small-strain shear modulus also in three different orientations. The obtained results confirm the anisotropic behaviour of Boom Clay. Moreover, the evolution of small-strain shear modulus with the distance from the gallery axis (r) was found to be similar to that of thermal conductivity: the values in the zone near the gallery are lower than those in the far field. From these experimental data, an extent of the excavation damaged zone (EDZ) of 4 m from the connecting gallery axis was determined. Further investigations on the microstructure of several samples taken at different distances r by mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) methods were carried out. Macro-pores of diameter ≥5 μm were identified in the samples near the gallery. The identified macro-pores were related to the effect of excavation damage, and a damage variable was thus defined, allowing a damage model to be developed. The values of the two model parameters have been determined from the observed relationship between macro-porosity and thermal conductivity. Comparisons between the predicted and experimental results in terms of small strain shear modulus and hydraulic conductivity show a reasonable agreement

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“…Zones of disturbed rock adjacent to deposition holes have been previously investigated with C-14-PMMA technique for granitic rock (Autio et al, 1998). The excavation disturbances in Opalinus clay have been investigated thoroughly on large scale with other techniques (Bossart et al, 2002(Bossart et al, , 2004 and its impact on the repository performance assessed (Blümling et al, 2007;Amann et al, 2015).…”

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confidence: 99%

Free radical polymerisation of methacrylates with thermal initiator in clay rock

Sammaljärvi

Rama

Ikonen

et al. 2016

Engineering Geology

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Clay rock porosity analysis with C-14-PMMA autoradiography was the focus of this work. Methodology for impregnating clay rock with C-14 labelled methacrylate, and fixing it via free radical polymerisation initiated with thermal initiator was developed towards this end. The effect of drilling was of particular interest because of their effect on the porosity and therefore they were studied in detail. Two different methacrylates were tested in this work. C-14 labelling enables measuring porosity through the autoradiography of samples impregnated with methyl methacrylate (MMA). The supporting analysis was done with thermogravimetric analysis (TGA), Scanning Electron Microscopy supplemented by energy dispersive X-ray spectrometry (SEM/EDAX) and X-ray diffraction (XRD). Procedures for impregnating clay rock and fixing C-14-labelled methacrylates in the sample were developed and optimised successfully. The two clay rock discs studied had mean porosities of (7.9 ± 0.8) % and (7.6 ± 0.8) % as measured by autoradiography. Autoradiography also shows that a disturbed zone can be seen as a region of high porosity in the drilled clay rock cores. In this case, the porosity of the disturbed zone is more or less double of the bulk porosity. TGA measurements gave bulk porosity values that varied between 4.1-15.0%. The TGA values were uncertain due difficulties associated with the sample matrix degrading at the same time as the methacrylate inside the sample. They could still be used to estimate the general range of the porosity. Pure MMA gave bulk porosity of (12.9 ± 7.5) % while mixture composed of 75% Hydroxyethyl methacrylate (HEMA) and 25% MMA gave a bulk porosity of (4.1 ± 6.0) %. SEM/EDAX results showed that calcite grains were more fractured than quartz grains in the disturbed zones. Quartz grains were mostly unaffected. This supports the conclusion that the porosity increase in the disturbed zone is intergranular and result of the break-up of calcite grains.

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Determination of the porosity, permeability and diffusivity of rock in the excavation-disturbed zone around full-scale deposition holes using the -PMMA and He-gas methods

Cited by 24 publications

References 1 publication

Measuring sorption coefficients and BET surface areas on intact drillcore and crushed granite samples

Measuring sorption coefficients and BET surface areas on intact drillcore and crushed granite samples

Impact of excavation damage on the thermo-hydro-mechanical properties of natural Boom Clay

Free radical polymerisation of methacrylates with thermal initiator in clay rock

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