Hydro-mechanical analysis of GMZ bentonite–sand mixtures in the water infiltration process as the buffer/backfill mixture in an engineered nuclear barrier

Abstract A series of unsaturated tests on the GMZ bentonite–sand mixture at different dry densities and sand ratios are analyzed. This mixture is proposed as buffer/backfilling material in the Chinese concept for radioactive waste disposal. The water retention properties were studied under both confined and unconfined conditions; the results show that the water retention capacity is independent of the confined conditions and dry density if the suction is greater that about 4–5 MPa, and by contrast, at low suctions ( 3 or sand ratio increasing from 30% to 50%, always lower than 2.0 × 10 − 12  m/s. Furthermore, the swelling pressure at different position of specimen was monitored during the infiltration process, and the dry density distributions have also been determined at the end of the tests. Therefore, this method can be used for engineering purposes to predict the unsaturated hydraulic parameters at an early stage of a design to get an idea of the required design and hence, cost.