Improvement in Reliability of the Long-Term Mechanical Behavior of Buffer Material

Takaji, Kazuhiko*; Shigeno, Yoshimasa*; Shimogochi, Takafumi*; Hirai, Takashi*; Shiratake, Toshikazu*

On the R&D of the high-level radioactive waste repository, it is essential that Engineered Barrier System (EBS) is stable mechanically over along period of time for maintaining each ability required to EBS. After closing the repository, the various external forces will be affected to buffer intricately for along period of time. So, to make clear the mechanical deformation behavior of buffer against the external force is important, because of carrying out safety assessment of EBS accurately. In this report, several sets of parameters are chosen for the previously selected two constitutive models, Sekiguchi-Ohta model and Adachi-Oka model, and the element tests and mock-up tests are simulated using these parameters. Through the simulation, applicability of the constitutive models and parameters is examined. Moreover, simulation analyses of EBS using these parameters were carried out, and mechanical behavior is evaluated over a long period of time. Analysis estimated the amount of settlement of the over pack, the stress state of buffer material, the reaction force to a base rock, etc., and the result that EBS is mechanically stable over a long period of time was obtained. Next, in order to prove analyses results a side, literature survey was conducted about geological age, the dynamics history of a Smectite layer. The outline plan was drawn up about the natural analogue verification method and preliminary examination was performed about the applicability of