Abstract
Safety of great deep repository design has been investigated for high-level radioactive waste disposal system in several countries such as Belgium, Canada, China, France, Germany, Japan, Sweden and Switzerland. The repository of the disposal is in most cases based on the concept of a multi-barrier system using the host rock barrier formation and a man-made barrier formation. The man-made barrier consists of high expansive bentonite. Thermal-hydro-mechanical behaviour simulation models were developed, including some parameters described by experimental works. The complex phenomena due to the transition into saturation and chemical reactions at the bentonite barrier system have been explained. This study focused on direct shear strength for compacted bentonite related to some factors induced by uncertainty problems such as hydration effect and pore-water pressure. Measured shear strength properties of compacted bentonite had been determined at high suction values. Also, it is clear that there is some influence of direct shear speed on direct shear strength both under unsaturated-saturated conditions. A modified direct shear apparatus was used in this study to observe changes in shear strength with increments of pore-water pressures.
Highlights
Safety of great deep repository design has been investigated for high-level radioactive waste disposal system in several countries [1, 2] such as Belgium, Canada, China, France, Germany, Japan, Sweden and Switzerland
This study focused on the shear strength in a direct shear apparatus for compacted bentonite related to some factors induced by uncertainty problems [10,11,12] such as hydration effect, gas pressure and pore-water pressure
This study was carried out using direct shear tests on a modified direct shear apparatus on both unsaturated bentonite and saturated bentonite at various shear rates
Summary
Safety of great deep repository design has been investigated for high-level radioactive waste disposal system in several countries [1, 2] such as Belgium, Canada, China, France, Germany, Japan, Sweden and Switzerland. The many mathematical models require lots of experimental test results to establish correct predictions for thermal-hydro-mechanical behaviour It is essential for the interpretation of phenomena in the barrier system to estimate the parameters regarding dominant factors [7,8,9] such as thermal, hydration, mechanical and chemical. This study focused on the shear strength in a direct shear apparatus for compacted bentonite related to some factors induced by uncertainty problems [10,11,12] such as hydration effect, gas pressure and pore-water pressure. A modified direct shear apparatus was useful to study the effect of porewater pressure in saturated bentonite [11, 12] This testing program focused on various pore-water pressures in saturated bentonite with different vertical stresses. Obtained relationship between pore-water pressures and direct shear strength will be obviously useful the estimation of bentonite barrier after long-time
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