Assessment on mechanical effect of engineering barrier system to fault movement

Hirai, Takashi; Tanai, Kenji ; Kikuchi, Hirohito*; Suzuki, Hideaki*; not registered; Onuma, Satoshi*

The objective of this report is to clarify mechanical effect of engineered barrier system to the unavoidable fault movement. From the basic policy of the second progess report by JNC, natural phenomenon which affect strongly to the geological disposal system shoult be avoided. However, small faults as sliprate "C" far from principal fault zone, are difficult to be found out completely. Therefore, it is important to evaluate the influence of these fault movements and to clarify stability and safety of the engineered barrier system. Accordingly, the effect of a rock displacement across a deposition holl was considered and the midium scale test was carried out. Then midium scale test was simulated by Finit Element Method in which the constitutive model of Tresca was adopted to analyze elastoplastic behavior of buffer material. From the result of the midium scale test and the analysis, it was realized that the buffer material diminish shear stress acting on the overpack. Further analytical study was conducted to evaluate the real scale engineered barrier system designed in the second progress report by JNC. From the study, it was apeared that stress in buffer corresponded to the stress calculated for the midium scale test model. Consequently, it was obvious that rock displacement, 80% of buffer thickness, didn't affect overpack if velocity of fault movement was under 10 cm/sec.