Investigation on hydraulic-mechanical properties in bentonite-sand mixture with consideration of salinity water

¹ Nuclear Facilities Division, Taisei Corporation, Tokyo, Japan.
² Department of Civil Engineering, Ashikaga University, Tochigi, Japan

^* nishimura.tomoyoshi@g.ashikaga.ac.jp

Abstract

Bentonite with fine components much such as extremely expansive soil has been commonly required as buffer/backfill materials in order to prevent seepage for construction of further deep geologicalrepository for disposal of high-level radioactive waste (i.e. HLW). The buffer received significant hydromechanical efforts from host rock at underground environment. While the construction/maintenance with long-time operation of a repository, it was predicted that high compacted bentonite will be progressively hydration due to pore water flow or infiltrated from surrounding host rock. The purpose of this study is to establish the connection among the basic mechanical properties, soil retention characters and chemical couple properties under unsaturated condition and saturated conditions for a bentonite-sand mixture. This conducted out some testing programs, which are soil-water characteristic curve test, unconfined compression test, creep test and triaxial compression test for unsaturated sodium bentonite sand mixture and saturated bentonite sand mixture. In addition, the influence of salinity water on mechanical properties is considered with comparison to saturated bentonite sand mixture subjected to swelled due to distilled water.