Bentonite homogenization analysis

WATER FLOW AND DIFFUSION PROBLEM IN BENTONITE MOLECULAR SIMULATION AND HOMOGENIZATION ANALYSIS... 

Abstract We here treat a diffusion problem coupled with water flow in bentonite. The remarkable behavior originates from molecular characteristics of its constituent clay mineral, namely montmorillonite, and we show the behavior based on a unified simulation procedure starting with the molecular dynamic (MD) method and extending the obtained local characteristics to a macroscale behavior by the multiscale homogenization analysis (HA Sanchez-Palencia. 1980). Not only the macroscale effective diffusion property but also the adsorption behavior is well defined based on this method. 

We here showed that for bentonite clay, we can determine the nano-scale material properties such as diffusion coefficient and viscosity by molecular dynamics (MD) simulation and extend the microscale characteristics to the macroscale behavior by the multiscale homogenization analysis (HA) method. A seepage flow and diffusion problem is treated. The micro/macro problem can be simulated well by this procedure if we know the microscale geometrical characteristics. 

We examine the problem of diffusion in a porous medium using a homogenization analysis (HA). Diffusion problems have important applications in environmental geosciences. We clarily the mechanism of diffusion, convective transport and adsorption in porous media at both the microscale and macroscale levels. Attention is particularly focused on diffusion processes in bentonite, which is an engineered geological barrier to be used to buffer the transport of radionuclides from deep geologic repositories. 

Long-Term Consolidation of Bentonite and a Homogenization Analysis of the Flow Field... 

Fujii N (2002) On diffusion problem in bentonite and homogenization analysis. Doctial thesis, Nagoya University (in Japanese)... 

Ichikawa Y, Kawamura K, Nakano M, Kitayama K, Kawamuia H (1998) Unified molecular dynamics/homogenization analysis for water flow in bentonite. In Proceedings of the 98 international high-level radioactive waste management conference, American Nuclear Society, Las Vegas, May 1998, pp 422-428... 

Ichikawa Y, Kawamura K, Fujii N, Theramast N (2002) Molecular dynamics and multiscale homogenization analysis of seepage/diffusion problem in bentonite clay. Int J Numerical Methods Eng 55 1 10... 

Ichikawa Y, Kawamura K, Theramast N, Kitayama K (2(X)4) Secondary and tertial consolidation of bentonite clay consolidation test, molecular dynamics simulation and multiscale homogenization analysis. Mech Mater 36 487-513... 

In this Section we first show that a local variation of viscosity in the pore water of a saturated smectitic clay such as montmorillonite or beidellite, which is a platelet crystal of about one nanometer (=10 m) thickness, can be calculated by a molecular dynamic (MD) simulation. Then, by applying the HA with the locally distributed viscosity, we can calculate the seepage field of the smectitic clay, which consists of stacks of clay minerals. Consequently, we apply a three-scale analysis of homogenization for a bentonite clay with quartz grains of about 10 [xm (1 fxm = 10 m). 

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