Modelling of soil mechanical stability and hydraulic permeability of the interface between coated biopore and matrix pore regions

Exudates and finer particles often coat the surface of biopores, increasing the mechanical stability and altering the physicochemical properties (e.g. wettability or sorption) of the surrounding. Properties of the biopore surface govern the macropore-matrix mass exchange processes during preferential flow in the soil macropores. However, the relationships between mechanical and hydraulic properties of coated biopore regions are not fully understood nor expressed by numerical models. Correlations between soil hydraulic and mechanical properties could perhaps be established by quantifying the water flow in defined pore structures of the biopore. The objective was to develop a model-based approach for studying the effects of clay-organic coatings on hydro-mechanical properties of biopore walls. The technical challenge was to develop a one-way directed solution (i.e., structural impact on fluid flow) between discrete element method (DEM) and a finite difference Stokes solver (FDMSS) to perform hydro-mechanical simulations of a coated biopore structure. Increasing the coating cohesion by DEM simulation to account for concentrating organo-mineral cementing agents, increased the overall stiffness as well as crack propagation through the soil matrix. As a result, biopore structure displayed higher yield strength and higher permeability through the interface between coating and matrix. Coating cohesion was positively correlated with Young's modulus and permeability displaying non-linear relationships. The one-way directed solution between DEM and FDMSS Stokes solver could be further extended to describe dynamic hydro-mechanical properties of more complex soil structures.

Automated summary

Exudates and finer particles often coat the surface of biopores, increasing mechanical stability and altering physicochemical properties. However, the relationships between mechanical and hydraulic properties of coated biopore regions are not fully understood nor expressed by numerical models.