Modelling reactive diffusion in clays with two-phase-informed pore networks

Qingrong Xiong, Andrey P Jivkov, Syed M Ahmad

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    Abstract

    Development of pore network models for reactive diffusion of various species in clays is presented. Networks are constructed using experimentally measured pore-space and solid-phase characteristics. This way incomplete geometrical and topological information for a given pore system can be balanced by known solid-phase properties. Opalinus Clay (OPA) is selected to demonstrate the application and validate the proposed model. OPA is modelled as anisotropic porous medium, reflecting preferential orientation of meso-porosity along clay bedding direction. Bulk diffusivities of various species (HTO, Cl- and I-) are calculated to investigate the effects of pore structure, anion exclusion and sorption. Sorption is simulated by changing the pore space, which is more realistic compared to existing reactive transport models with assumed constant pore geometry. Anion exclusion effects are simulated by introducing diffuse double layer (DDL) in the model. Results agree well with experimentally measured diffusion coefficients for transport parallel and perpendicular to the bedding direction. The proposed model is applicable to a large class of geo-materials and suitable for linking to lattice models for deformation and damage.
    Original languageEnglish
    Pages (from-to)222-228
    Number of pages6
    JournalApplied Clay Science
    Volume119
    DOIs
    Publication statusPublished - 15 Jan 2016

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