The thermal consolidation of Boom clay

When a mass of saturated clay is heated, as in the case of host soils surrounding nuclear waste disposal at great depth, the thermal expansion of the constituents generates excess pore pressures. The mass of clay is submitted to gradients of pore pressure and temperature, hydraulic and thermal flows, and changes in its mechanical properties. In this work, some of these aspects were experimentally studied in the case of Boom clay to help predict the response of the soil, in relation to investigations in the Belgian underground laboratory at Mol. Results of slow-heating tests with careful volume change measurements showed that a reasonable prediction of the thermal expansion of the clay-water system was obtained by using the thermal properties of free water. Despite the density of Boom clay, no significant effect of water adsorption was observed. The thermal consolidation of Boom clay was studied through fast-heating tests. A simple analysis shows that the hydraulic and thermal transfers are uncoupled. Experimental results from fast-heating tests showed that the consolidation coefficient does not change significantly with increased temperature, due to the opposite effect of increasing permeability and decreasing porosity. The changes of permeability with temperature were investigated by running constant head measurements at various temperatures. An indirect analysis, based on estimation of the coefficient of volume change mv, showed that the indirect method of estimating the permeability from consolidation tests should be considered carefully. Intrinsic permeability values were derived by considering the change of the viscosity of free water with temperature. A unique relationship between the intrinsic permeability and the porosity was observed, with no dependence on temperature, confirming that the flow involved in the permeability test only concerns free water.Key words: clays, thermal consolidation, adsorbed water, permeability, temperature effects, radioactive waste disposal.

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Spatial variation in porosity and permeability of the Rupel Clay Member in the Netherlands

Netherlands Journal of Geosciences – Geologie en Mijnbouw ◽

10.1017/njg.2016.28 ◽

2016 ◽

Vol 95 (3) ◽

pp. 253-268 ◽

Cited By ~ 2

Author(s):

Hanneke Verweij ◽

Geert-Jan Vis ◽

Elke Imberechts

Keyword(s):

The Netherlands ◽

Spatial Variation ◽

Clay Content ◽

Burial Depth ◽

Southeastern Part ◽

Boom Clay ◽

The North ◽

Sealing Capacity ◽

Porosity And Permeability ◽

Permeability Data

AbstractThe spatial distribution of porosity and permeability of the Rupel Clay Member is of key importance to evaluate the spatial variation of its sealing capacity and groundwater flow condition. There are only a limited number of measured porosity and permeability data of the Rupel Clay Member in the onshore Netherlands and these data are restricted to shallow depths in the order of tens of metres below surface. Grain sizes measured by laser diffraction and SediGraph® in samples of the Rupel Clay Member taken from boreholes spread across the country were used to generate new porosity and permeability data for the Rupel Clay Member located at greater burial depth. Effective stress and clay content are important parameters in the applied grain-size based calculations of porosity and permeability.The calculation method was first tested on measured data of the Belgian Boom Clay. The test results showed good agreement between calculated permeability and measured hydraulic conductivity for depths exceeding 200m.The spatial variation in lithology, heterogeneity and also burial depth of the Rupel Clay Member in the Netherlands are apparent in the variation of the calculated permeability. The samples from the north of the country consist almost entirely of muds and as a consequence show little lithology-related variation in permeability. The vertical variation in permeability in the more heterogeneous Rupel Clay Member in the southern and east-southeastern part of the country can reach several orders of magnitude due to increased permeability of the coarser-grained layers.

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Twenty-five years' geotechnical observation and testing in the Tertiary Boom Clay formation

Géotechnique ◽

10.1680/geot.2007.57.2.229 ◽

2007 ◽

Vol 57 (2) ◽

pp. 229-237 ◽

Cited By ~ 56

Author(s):

F. Bernier ◽

X. L. Li ◽

W. Bastiaens

Keyword(s):

Boom Clay ◽

Clay Formation

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Consolidation thermique par chaleur d'un sol non saturé

Canadian Geotechnical Journal ◽

10.1139/t91-005 ◽

1991 ◽

Vol 28 (1) ◽

pp. 42-50 ◽

Cited By ~ 15

Author(s):

C. Saix

Keyword(s):

Unsaturated Soil ◽

Constitutive Law ◽

Saturated Soils ◽

Soil Consolidation ◽

Thermal Compression ◽

Triaxial Apparatus ◽

Thermal Consolidation ◽

Sol Non Saturé ◽

Temperature Parameter ◽

Definition Of

The thermal consolidation by heating of an unsaturated silty soil is studied by means of six tests performed in a thermal triaxial apparatus. The results show the importance of the temperature parameter and a clear similarity with the classical consolidation tests on saturated soils. A constitutive law is proposed for the thermal consolidation by heat that allows the definition of indices of thermal compression. This law is used to calculate the displacements in an unsaturated fill for heat storing. Key words: unsaturated soil, consolidation, heat, triaxial, modelling. [Translated by the Journal]

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Neptunium Speciation in Humic Acid-rich Clay Water upon Interaction With Radioactive Waste Glass Samples

MRS Proceedings ◽

10.1557/proc-757-ii7.1 ◽

2002 ◽

Vol 757 ◽

Cited By ~ 3

Author(s):

V. Pirlet ◽

P. Van Iseghem

Keyword(s):

Humic Substances ◽

Humic Acids ◽

Specific Interaction ◽

Waste Glass ◽

High Level Waste ◽

Boom Clay ◽

Dissolution Tests ◽

Vis Spectroscopy ◽

Doped Glasses ◽

High Level

ABSTRACTOrganic complexes of actinides are known to occur upon interaction of high level waste glass and Boom Clay which is a potential host rock formation for disposal of high level waste in Belgium. The solubility and mobility of 237Np, one of the most critical radionuclides, can be affected by the high dissolved organic carbon content of the Boom Clay porewater through complexation with the humic substances. The influence of humic substances on the Np behaviour is considered through dissolution tests of Np-doped glasses in Boom Clay water and through fundamental study of the specific interaction between Np(IV) and the humic acids using spectroscopic techniques. High Np(IV) concentrations are found in the glass dissolution tests. These concentrations are higher than what we should expect from the solubility of Np(OH)4, the solubility limiting solid phase predicted under the reducing conditions and pH prevailing in Boom Clay. Studying the specific interaction of Np(IV) with humic acids in Boom Clay porewater, high soluble Np concentrations are also measured and two main tetravalent Np-humate species are observed by UV-Vis spectroscopy. The two species are interpreted in terms of mixed hydroxo-humate complexes, Np(OH)xHA with x = 3 or 4. These species are the most likely species that can form according to the pH working conditions. Using thermodynamic simplified approaches, high complexation constants, i.e. log β131 and log β141 respectively equal to 46 and 51.6, are calculated for these species under the Boom Clay conditions.Comparing the spectroscopic results of the dissolution tests with the study of the interaction of Np(IV) with humic substances, we can conclude that the complexation of Np(IV) with the humic acids may occur and increases the solubility of Np(OH)4 upon interaction of a Np-doped glass and the Boom Clay porewater.

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