Estimating thermo-osmotic coefficients in clay-rocks: II. In situ experimental approach.
Water flow in compacted shales is expected to be modified by thermo-osmosis when a thermal gradient exists. However this coupled-flow process is poorly characterized since no experiments on non-remoulded clay-rocks are found in the literature. This paper presents a set of thermo-osmosis experiments carried out in an equipped borehole installed in the Liassic argillite at the Institut for Radiological protection and Nuclear Safety (IRSN) underground research laboratory (URL) of Tournemire (southeastern France). A numerical model - including coupled-flow equations, mass conservation laws, thermal expansion and changes of water properties with temperature - was developed for the interpretation of these experiments. A thermo-osmotic response was deduced from the pressure evolution in the test interval after temperature pulses (+2.5, +5.1, and +9 degrees C). The values of thermo-osmotic permeability determined during the experiments range between 6x10(-12) and 2x10(-10)m(2)K(-1)s(-1), depending on the pulse temperature and uncertainties on the model parameters. A sensitivity analysis on several model parameters was performed to constrain these uncertainties.
Institut de Radioprotection et de Sûreté Nucléaire, IRSN/DEI/SARG/LR2S, BP 17, F-92262 Fontenay-aux-Roses, France. joachim.tremosa@irsn.fr
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Gonçalvès
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Matray
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