Experimental study of swelling pressure of compacted bentonite-sand mixture

Compared with pure bentonite, bentonite-sand mixture can be used as buffer material in HLW geological disposal to provide low permeability, high thermal conductivity and good workability. Laboratory tests were conducted on compacted mixture of GMZ001 bentonite and quartz sand in different additions of 0, 10%, 20%, 30%, 40% and 50%. Test results show that the liquid limit and plastic limit of the mixture decrease linearly with the increase of sand addition percentage. The maximum swelling pressure of the mixture is exponential increase with initial dry density; but decreases slender with initial water content while the initial water content is higher. By introduction of the concept of effective clay density, an optimum model has been established to describe the relationship between swelling pressure with sand addition percentage and dry density under a certain water content, so as to provide a useful tool for predicting and controlling the swelling pressure of the GMZ001 bentonite and sand mixture in practice.