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The swelling pressure of bentonite and sand mixtures
KTH, School of Chemical Science and Engineering (CHE).
2013 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The compacted bentonites are used as buffer and backfill materials for engineering

barriers for high-level nuclear waste repositories located underground. For this

purpose, it is very important to evaluate the swelling characteristics of this clay.

The swelling capacity is one of the most important properties of the bentonite clay. The

swelling behaviour is due two mechanisms, the crystalline swelling and the osmotic

swelling. These mechanisms produce an increase in the distance between the layers of

montmorillonite which is one component of bentonite.

The result of the swelling capacity is the swelling pressure. It has been studied in

several investigations. The results of experimental tests have been collected and

compared in this thesis, considering only the Na-dominant bentonite and sand and

distilled water as test solution.

The experimental tests show that there is only an unique relation between different

bentonites in the Na-dominant bentonite and sand mixture swollen depending on its

final dry density. Also, the relation between the swelling pressure and the clay void

ratio shows the mechanism of the swelling pressure.

On the other hand, a mechanistic model is used to predict the swelling pressure of fully

saturated bentonite and sand mixture in distilled water. Firstly, it has been compared

with the results of experimental tests and it should be pointed out that the model gives

good predictions.

In addition, the model has been used to make sensitivity analysis with different

parameters of bentonite. The most important conclusions in this section show that the

swelling pressure mainly depends on the distance among particles. Also, the sensitivity

analyses indicate which parameters should be fitted more carefully for future studies to

validate this model with different bentonites.

Place, publisher, year, edition, pages
2013. , 46 p.
Keyword [en]
Swelling pressure; bentonite and sand mixture; crystalline swelling; osmotic swelling; mechanistic model; montmorillonite.
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-158511OAI: diva2:777909
Available from: 2015-01-09 Created: 2015-01-09 Last updated: 2015-01-09Bibliographically approved

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