Özet:

Bentonites and sand-bentonite mixtures are usually used for impervious barriers at nuclear waste repositories, municipal solid waste landfill liners, etc. These mixtures should be able to perform for a long time without changing their strength and hydraulic conductivity properties. The literature studies have shown that high temperature and thermal cycles have negative effects on the hydraulic conductivity and strength of soils. For example, hydraulic conductivity increases in the presence of high temperature. For that reason, the resistivity of bentonites and sand-bentonite mixtures should be increased against high temperatures when they are used in liners. Boron minerals are used in order to increase the thermal resistivity of materials in industry. Hence the boron mineral namely; ulexite can be added to the sand-bentonite mixtures in order to improve strength and hydraulic conductivity properties of these mixtures against high temperature or thermal cycles. In this study, the compaction, consolidation, hydraulic conductivity and shear strength properties of ulexite added sand-bentonite mixtures were investigated at room temperature. Additionally, the shear strength behavior of ulexite added sand-bentonite mixtures was investigated under high temperature (80°C). The sand-bentonite mixtures were prepared which contains 10% bentonite by weight. The 10% and 20% ulexite were added to these mixtures. The mixtures were prepared according to the compaction test results (dry unit weight and optimum water content+2%). According to the test results, as the ulexite additive decreased the optimum water content value and increased the maximum dry unit weight. When the ulexite was added to the sand-bentonite mixtures, amount of the total vertical strain (compressibility) increased as the ulexite percentage increased. The maximum shear stress value of sand-bentonite mixtures in the presence of ulexite at 80°C was generally higher than those of at room temperature.

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