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Investigations of Kinnekulle K-bentonite aimed at assessing the long-term stability of bentonites under repository conditions


The mineral formula, the content of fixed potassium and the average interlayer charge of the montmorillonite-illite mixed layer part of four Ordovician K-bentonite samples from Kinnekulle (Sweden) were investigated. The content of fixed potassium was found to decrease from 84% to 50% with increasing depth and distance from the Permian basalt intrusion about 100m above the bentonite beds. The interlayer charge of the mixed layer is smectitic, i.e. below 0.5 charges per formula unit. The swelling pressures of air-dried, gently grinded and uniaxially compressed specimens with dry densities between 1.5Mg/m3 and 2.0Mg/m3 range from 1N/mm2 to 15N/mm2. This is about 20% of the swelling pressure values of identically treated Ca-montmorillonite. Following ultrasonic treatment, air-drying, gently grinding and compaction, increased swelling pressures of about 70% of those of Ca-montmorillonite were obtained. The reason for this increase in swelling pressure was investigated by dispersion experiments and determinations of water vapour adsorption isotherms of ultrasonically treated and untreated material.


Müller-Vonmoos, Max and Kahr, Günter and Bucher, Felix and Madsen, Fritz

Index Terms:

Soil; SoilGroup; Bentonite; Swelling

Further Information:

Date published: 1990