The role of diffusion incontaminant migration through soil barriers

 

This paper describes the role of diffusion in governing the transport of contaminants through soil (mineral) barriers (e.g., soilliners and slurry walls). The specific topics covered include the significance of diffusive transport through porous media, the relative significance of the various parameters affecting contaminant migration, and the effects of various modelling assumptions for the design of soil barriers.

 

This paper describes the role of diffusion in governing the transport of contaminants through soil (mineral) barriers (e.g., soilliners and slurry walls). The specific topics covered include the significance of diffusive transport through porous media, the relative significance of the various parameters affecting contaminant migration, and the effects of various modelling assumptions for the design of soil barriers.

Charts for preliminary design utilizing dimensionless parameters are presented for the purpose of illustrating the role of diffusive transport through soil barriers for both transient and steady·state conditions for three different waste containment scenarios: (1) pure diffusion, (2) diffusion and advection in the same direction, and (3) diffusionlagainst advection.

The design charts allow for analyses to determine the basic features of a barrier referring to either contaminant concentration or contaminant mass flux. The analyses show that a low hydraulic conductivity for the soil is a necessary, but not sufficient, condition for the design of a successful barrier, Failure to recognize the role of diffusion in barrier design can lead to extremely unconservative designs. The assumption of steady-state seepage flow of the solvent (water) and the boundary conditions employed in the analysis methods are shown to be approximations for actual field conditions, but are useful in terms of providing simplified assessments of barrier performance.

Emphasis is placed on conservative assumptions when the proposed analytical models are used. A laboratory method for measuring effective diffusion coefficients and the application of measured values for design of soil barriers also are illustrated.


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AUTORI: Manassero M.,Shackelford C.D.
RIG ANNO:1993 NUMERO:1
Numero di pagine: 5


Allegato: https://associazionegeotecnica.it/wp-content/uploads/2010/11/RIG_1994_1_5.pdf
Allegato:
Articolo completo: https://associazionegeotecnica.it/wp-content/uploads/2010/11/RIG_1994_1_5.pdf