EXPERIMENTAL RESULTS ON THE EFFECT OF TEMPERATURE ON THE HYDRO-MECHANICAL BEHAVIOUR OF BENTONITE
The bentonite barrier of underground repositories for high-level radioactive waste will be hydrated by the groundwater while it is subjected to high temperatures due to the radioactive decay of the wastes. These temperature changes affect the hydraulic and mechanical response of the bentonite, what has important implications on the design and performance of the repository. The experimental research reported in this paper is on the influence of temperature on the hydro-mechanical behaviour of bentonite, and has been carried out with the Spanish FEBEX bentonite compacted at dry densities expected in the repository (from 1.3 to 1.8 g/cm3). The dependence of the swelling strains of bentonite on temperature has been measured in the interval from 30 to 80℃. At high temperatures the swelling capacity of the clay slightly decreases. Also, a clear decrease of swelling pressure as a function of temperature was observed for the same dry densities. Nevertheless the deformation of bentonite is more dependent on the stress than on temperature. It has also been detected an increase with temperature in the water saturated permeability of bentonite. The retention curves of the bentonite compacted at different dry densities have been determined under isochoric conditions and in the range of temperatures between 20 and 120℃. For a given density and water content, suction decreases as temperature increases at a rate that is larger than the one predicted on the basis of the water surface tension change with temperature. Mechanisms related to the physicochemical interactions that take place at microscopic level-in particular the transfer of interlayer water to the macropores triggered by temperature-seem to explain qualitatively the experimental observations.
bentonite temperature swelling permeability water retention capacity
M.V. Villar R. Gomez-Espina A. Lloret
CIEMAT, 28040 Madrid, Spain UPC, 08038 Barcelona, Spain
国际会议
上海
英文
272-280
2009-08-24（万方平台首次上网日期，不代表论文的发表时间）