On the thermal hydro mechanical chemical behavior of bentonite sand mixture

Department of Civil Engineering, Ashikaga University, Tochigi, Ashikaga, Japan

^* Corresponding author: nishimura.tomoyoshi@g.ashikaga.ac.jp

Abstract

The concept to high-level radioactive waste (HLW) repository generally involves anengineering-artificial barrier system, in which hardly compacted bentonite sand mixture blocks are placed carefully around the waste canister, and the canister is of stiffness in the design. Placed the bentonite sandmixture blocks, gradually receive hydration due to groundwater. Thermal-hydraulic-mechanical-chemical phenomena of compacted bentonite sand mixture after wetting, suction change and thermal effort are a critical parameter for buffered system This study proposes the influence of suction, relative humidity and thermal effort in thermal-hydraulic on deformation properties and mechanical properties for bentonite-sand mixture. A series of testing programs are prepared such as calibration test for changing of relative humiditywith temperatures, measurement of volume change involving heating and changing of suction, determination of unconfined compressive strength, for thermal performance triaxial compression tests for both unsaturated bentonite sand mixture and saturated bentonite sand mixture. The obtained results are further interesting, and summary provide as following. To suction increment incorporation with thermal heating produce induces obviously shrinkage of the bentonite sand mixture, and lead the decrement of strength. Elevated temperature confirm further reduction for maximum deviator stress using a developed triaxial compression apparatus that is regardless of unsaturated condition and saturated condition.