Analysis of Case with Change of Density of Buffer Material by Extrusion Behavior to Use Diffusion Model

Matsumoto, Kazuhiro*; Tanai, Kenji ; Kanno, Takeshi*; Iwata, Yumiko*

The buffer that will be used as a component of the engineered barriers system swells when saturated by groundwater. As a result of this swelling, buffer may penetrate into the peripheral rock zone surrounding the buffer through open fractures. It sustained for extremely long periods of time, the buffer extrusion could lead to reduction of buffer density, which may in turn degrade the assumed performance. In this report, the viscosity of bentonite was measured as one of the parameter of diffusion model. In addition, the simulation analysis was carried out to confirm the applicability of diffusion model. Moreover, an analytical evaluation on extrusion behavior of buffer into rock fractures was performed due to estimate the long-term stability of buffer as reduction of density.