The Future plan on extrusion experiment of bentonite buffer

Matsumoto, Kazuhiro*; Tanai, Kenji 

The bentonite will be resaturated and swelled gradually after repository closure, not only will any gaps within the bentonite sealed, but the bentonite may also be excluded into fractures in the surrounding rock, diverting a part of the water flow away from the repository. However, if loss of bentonite into fractures due to extrusion is too pronounced, then the decrease in density of the bentonite within the repository may lead to reduce its favourable properties. In this study, the extrusion behavior of bentonite into the artificial fracture of the acrylic cell was investigated in consideration of flow velocity, aperture and dry density of bentonite specimen until present day. In future, experiments will be carried out to clarify the realistic behavior of extrusion phenomenon in consideration of roughness of fracture. This paper present existing results and future plan of test.