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Abstract It is proposed that a mixture of bentonite and quartz sand might be a suitable backfill/buffer material for HLW disposal in China after reviewing the foreign research results，because bentonite can be optimized by addition of certain content of quartz sand to improve the heat conductivity and mechanical strength without an obvious increase in permeability. The compaction properties of GMZ001 bentonite-sand mixtures with a series of sand additions ranging from 0% to 50% are studied by standard and modified proctor compaction tests，and the static compaction tests under 20 MPa and 50 MPa pressures are designed. Test results show that the relationship between maximum dry density and optimum water content follows the same power function for all of the mixture specimens prepared in different compaction methods with different compaction efforts，while linear correlations exist for mixture specimens prepared in different compaction methods and compaction efforts. These correlation functions provide useful tools for convenient selection of compaction methods in practice. It is concluded that addition of 10%–30% quartz sand to GMZ001 bentonite can improve the compaction quality without altering the estimated impermeability of the backfill/buffer material.
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Received: 16 March 2009
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