MECHANICAL CHARACTERISTICS AND WATER RETENTION PROPERTIES OF UNSATURATED “BENTONITE-BASED ENGINEERED BARRIER MATERIALS” BASED ON CONTROLLED-SUCTION TESTS

Abstract

Bentonite-based engineered barrier materials transfer from unsaturated state as emplaced to saturated state after closure of deep geological disposal facilities for radioactive waste, while decrease in saturation could occur due to heat and gas generation from the wastes. Modelling for mechanical characteristics and water retention properties of unsaturated “bentonite-based engineered barrier materials” are indispensable to predict such important transient behavior. In this study the following characteristics are obtained based on controlled-suction oedometer or triaxial compression tests : i) swelling and shrinking caused by respectively wetting and drying, ii) consolidation under constant matric suctions, iii) shear strength depending on matric suction, iv) hysteresis of water retention. In addition, applicability of existing constitutive models such as Barcelona basic model, Komine’s model, vG model, and suction stress concept are discussed based on these results.