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Workreport 2020-6



Numerical Modelling of Isostatic Compression


Fortino, S., Sjöblom, V., Gharbieh, H., Löija, M.



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This report is published only for Posiva's internal use.

The numerical work presented in this report was developed to support the experimental research on isostatic compression of buffer blocks of bentonite MX-80 carried out at VTT during 2013-2015. The modelling at the macroscale was first developed for small specimens tested in 2013 and was further improved for the design of a full block in 2014. The same model was then used to analyse the full-scale disk block and ring built at VTT in 2015.

The assessment of a material model, developed for both the mechanical behaviour and the air pressure effect under isostatic compression, can be a useful numerical tool to support the experimental research in order to avoid extensive laboratory testing. In particular, the related numerical analysis is useful to understand the structural behaviour of small and medium scale experiments, as well as to assess the dimensions and the loading curves to be adopted for the preparation of full-scale isostatic blocks.

Finally, a microscale modelling of bentonite was also developed to study the role of the material microstructure during isostatic unloading, in order to have a better knowledge about the crack initiation and development in the isostatic blocks. This part has to be considered as a preliminary work for future improvement of microscale models for bentonite.


Isostatic compression, material modelling, macroscale and microscale structural analysis, Abaqus code



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