Databank

POSIVA Report 2012-49

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Name:

Thermo-Hydro-Mechanical Tests of Buffer Material

Writer:

Pintado, X., Md. Mamunul, H. & Martikainen, J.

Language:

English

Page count:

152

ISBN:

ISBN 978-951-652-231-2

Summary:

MX-80 bentonite is the reference clay material for the buffer component planned to be used in the deep geological repository for the disposal of spent nuclear fuel in Finland. The buffer presents complex thermo-hydro-mechanical behavior which is modeled with different constitutive models for heat flow, water flow and stress-strain evolution in the buffer.

 Thermo, hydro and mechanical models need parameters to evaluate the THM-behavior. These modeling parameters were determined by performing series of laboratory experiments as follows:

 •          Water retention curve tests were performed on compacted bentonite samples, encompassing a range of initial dry density values from 1397 to 1718 kg/m3 as the initial water content was around of 5-8%. The water retention curve was determined by imposing different suctions to the samples and the suctions were then checked using capacitive hygrometer and chilled mirror psychrometer.

 •          Oedometer tests were performed on compacted bentonite samples, encompassing a range of initial dry density values from 1590 to 1750 kg/m3 as the initial water content was around of 6%.  Samples were saturated with tap water, 35 or 70 g/L salt solutions.

 •          Infiltration tests were performed on compacted unsaturated bentonite samples, encompassing a range of initial dry density values from 1400 to 1720 kg/m3 as the initial water content was approximately between 4-7 %.  Samples were saturated with tap water, 0.87, 35 or 70 g/L salt solutions.

 •          Tortuosity tests were performed on bentonite samples, encompassing a range of dry density values from 1460 to 1750 kg/m3 and the degree of saturation varied between 33-93 %.  

 •          Thermal conductivity tests were performed on compacted bentonite samples, encompassing a range of dry density values from 1545 to 1715 kg/m3 and the degree of saturation varied between 31-88 %. The measurement was performed using a thermal needle probe.

The general trend of all analyzed parameters was as expected when dry density, water content, and composition of saturating solutions were varied.

Keywords:

Buffer, water retention, suhygrometer, psychometer, oedometer, stress-strain, infiltration, suction, tortusosity, thermal conductivity.

File(s):

Thermo-Hydro-Mechanical Tests of Buffer Material (pdf) (26.9 MB)


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