Towards functional characterization of soil pore size distribution using shear-thinning fluids: challenges and prospects

Due to the immense complexity of porous structure of soils, a proper level of complexity reduction is fundamental to any continuum modeling approach, ranging from one parameter characteristics, such as the Darcy law, to the overwhelming virtual representations, such as pore network models or even full-pore-space geometry characterisations. The role of various levels of reduced descriptions is crucial not only for the practical purpose of representing and simulating the particular functional behavior of given soil based on measurable properties, but also because they may inspire our understanding of the processes involved and, in particular, the changes and interaction of various soil properties.

We are interested in non-Newtonian porosimetry approach, introduced previously by other authors, which allows quantifying the functional pore size distribution of porous medium based on saturated flow experiments using (yield-stress and/or) shear-thinning fluids, such as xanthan gum aqueous solutions. The functional pore size distribution has been defined by the capillary bundle model of the flow through the porous medium and is related to various other (saturated and unsaturated) hydrological properties of the soil. The framework offers interesting potential applications both in the laboratory and in field, as it allows for nondestructive measurements that are not restricted to very small samples. In the poster, we focus on the method introduced previously by (Abou Najm, Atallah, 2016). We will discuss some interesting aspects of the concept (such as the relation to different definitions of pore size) along with some related issues (such as the sensitivity of the inverse problem to the measurement errors or the observed polymer entrapment). We will also touch on more potential applications, such as (Slavík, Lanzendörfer, 2024).

Abou Najm, M.R., Atallah, N.M., 2016. Vadose Zone Journal 15. https://doi.org/10.2136/vzj2015.06.0092
Slavík, M., and Lanzendörfer, M. 2024. Hydrology 11(9):133. https://doi.org/10.3390/hydrology11090133