ABSTRACT
A certainly design, construction, management and observation of geological repositories is crucial key to address the safety disposal of radioactive waster including LLWs and HLWs. This study focused on dynamic properties for unsaturated-saturated bentonite sand mixture used as one of engineered barrier system, which composed sodium bentonite and silica sand. Cyclic triaxial apparatus is used for determination of reduction amplitude stress, stress-strain behaviour and changing of cyclic stress ratio. Also, shear strength parameters are measured from monotonic loading tests for unsaturated-saturated bentonite sand mixture, which are angle of shear resistance and apparent cohesion, and failure envelopes are estimated, proceeding of faire conditions are observed in between principal means stress and principal deviator stress. Specimens used in this study are unsaturated condition and saturated condition, and unsaturated specimens are applied high suction controlling by vapor pressure technique in order to prepare variety of soil moisture and various of dry density. Owing suction control by vapor pressure technique, it proves that specimens have hydration effect associated to strength parameters and stress-strain properties in dynamic loading. Also, it is found out that accumulated axial strains for unsaturated bentonite sand mixture with various of high suctions verified the influence of initial cyclic stress ratio and suction value, and accumulated axial strains are slightly when suction is over 83 MPa. Other hands, specimens are decrement to the resistance in cyclic loading due to increment of soil moisture induced by relative humidity of 98%, and strains in compression side.
