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Takayama, Yusuke; Tachibana, Shinya*; Iizuka, Atsushi*; Kawai, Katsuyuki*; Kobayashi, Ichizo*
Soils and Foundations, 57(1), p.80 - 91, 2017/02
Times Cited Count：11 Percentile：48.47(Engineering, Geological)Bentonite has remarkable swelling characteristics and low permeability that makes it a suitable buffer material in a purpose built repository for the geological disposal of radioactive waste. It is necessary to use reliable numerical simulation techniques to demonstrate that the repository is safe and mechanically stable for tens of thousands of years. Constitutive model that describes the mechanical behavior of bentonite is a key technique in such numerical simulations. The current paper proposes a constitutive model for bentonite, which treats bentonite as an unsaturated elasto-plastic material that changes its mechanical properties as it becomes saturated. In the proposed model, the swelling index and an expression formula for negative dilatancy are treated as functions of degree-of-saturation. Montmorillonite content is used as an input parameter in the proposed model and so is applicable to a variety of bentonite based materials of varying montmorillonite content. Experimental results from swelling volume and swelling pressure tests taken from the literature are shown to be satisfactorily predicted by the proposed model.
Kishida, Kiyoshi*; Sawada, Atsushi; Yasuhara, Hideaki*; Hosoda, Takashi*
Soils and Foundations, 53(1), p.105 - 116, 2013/02
Times Cited Count：22 Percentile：63.11(Engineering, Geological)Considering the safe, long-term sequestration of energy byproducts, such as radioactive waste, one of the important parameters is the groundwater flow velocity through the void of rock masses and/or fractures. In this research work, two-dimensional seepage flow analyses, using the authors' proposed 2D model, with considering the inertia term, are carried out for single fracture permeability tests under conditions which allow for the application of the cubic law. In comparing the results of the experiments with the numerical simulations, the results of the simulation show a good agreement with the experimental results. From these simulation results, the fracture flow of an inhomogeneous structure is discussed, along with the local Reynolds number, and the resistance through the fracture geometry is considered. Consequently, under the condition of a mean Reynolds number of less than 1.0, the inertia terms cannot affect on the fracture flow, but the hydraulic resistance can affect.
