DEPARTMENT OF PHYSICS WWW.JYU.FI/FYSIIKKA/EN

DEPARTMENT OF PHYSICS
WWW.JYU.FI/FYSIIKKA/EN
X-ray tomographic method for measuring three-dimensional
wetting and deformation of compacted bentonite
Tero Harjupatana, Jarno Alaraudanjoki, Markku Kataja and Aaro Eloranta, Dept of Physics, University of Jyväskylä, Finland
Mika Laitinen and Antti Niemistö, Numerola Oy, Jyväskylä, Finland
The objective of this on-going work is to obtain direct 3D data for validating numerical models of wetting and hydromechanical behaviour of bentonite buffer during the initial wetting phase. To this end, nondestructive methods based on Computed X-ray microtomography (CT) were developed for simultaneous monitoring of water transport and the resulting swelling deformation in small-scale
bentonite samples. The method was first applied in compacted cylindrical samples of purified bentonite placed and sealed in a closed
sample holder that allows wetting of the sample through a sintered ceramic block, measurement of swelling pressure and periodical
tomographic imaging using a table-top CT scanner. The evolution of water content and material displacement between consequtive
images is the found using specific 3D image analysis techniques.
EXPERIMENTAL SET-UP
Force sensor
20 mm
Venting channel
Plastic tube (PEEK)
sample
X-ray beam
Sintered blocks
Bentonite sample
rotation
Table-top X-ray tomographic scanner
Sample holder in X-ray beam
Wetting channel
Schematic of the sample holder
Compacted bentonite sample
MONITORING TRANSPORT OF WATER IN 3D
7h
46h
185h
The measured water content at various times of wetting process illustrated as a transparent color field for a compacted bentonite sample. The images shown are 3D X-ray tomographic difference images of the wetted state and the original dry state. Only one half of the cylindrical sample is shown. The water inlet (sintered block) is visible at the bottom face of the sample.
FINAL RESULT: Water content and deformation
Water content [%]
3D DEFORMATION DUE TO SWELLING
The measured displacement field in a swelling bentonite sample obtained by a
3D image correlation method.
Water content and displacement field averaged over the azimuthal angle at various
instants of time - to be compared with model predictions.