Research on the mechanical characteristic of the bentonite mixture material under the groundwater environment of Horonobe

Takaji, Kazuhiko*; Shigeno, Yoshimasa*; Shimogochi, Takafumi*

In the Horonobe underground research project, a creep examination of a rock and buffer material, a tunnel closing examination, a fixed accuracy confirmation examination and a T-H-M-C examination, etc. is planned. These field examinations are aimed at the illustration and evaluation of applicability of the Engineered Barrier System (EBS) design method under the detailed geological environment shown in the H12 report, understanding of long-term phenomenon for EBS, and improvement in reliability of the prediction method. Then, in order to examine the specifications of the bentonite mixture material in design of a field test, the in-situ examination using artificial groundwater which imitated the groundwater of Horonobe and NaCl solution was carried out, and the mechanical behavior of the bentonite mixture material under the sea water environment assumed in the location of the field examination in Horonobe has been grasped. Moreover, in order to confirm the applicability of the prediction technique of the long-term behavior of an engineered barrier, overpack sinking behavior using the result of an in-situ examination etc. was analyzed.