A new approach for determining effective soil hydraulic functions

Abstract

Summary We investigated the possibility of inferring effective hydraulic properties of soil from the structure of the pore space. The aim was to identify structural properties, which are essential for water flow, so that physical experiments may be replaced by direct morphological measurements. The pore structure was investigated in three dimensions by serial sections through impregnated samples. The complex geometry of pore space was quantified in terms of two characteristics: pore‐size distribution and pore connectivity. Only pores larger than 0.04 mm were considered. The results were used as input parameters for a pore‐scale network model. The main desorption branch of the soil‐water characteristic and the corresponding hydraulic conductivity function of the network model were calculated by numerical simulation. The simulation results, which are exclusively based on morphological investigations, were compared with independently measured results from a multi‐step outflow experiment. This approach was demonstrated for two centrasting soil materials: the A and B horizons of a silty agricultural soil. The simulations were close to the experimental data, except for the absolute values of the hydraulic conductivity. The pore‐size distribution and pore connectivity govern the shape of hydraulic functions and the applied morphometric methods are suitable for predicting essential characteristics of hydraulic soil properties.

Coupling X-ray microtomography and macroscopic soil measurements: a method to enhance near-saturation functions?

“…7), we can still observe along F1 the ranking CT < RT2 < RT1, which is the reverse order as compared to macroporosity conductivity efficiency. Vogel and Roth (1998) demonstrate that realistic pore network representation has to take into account its connectivity and tortuosity. Our PCA is consistent with their results since specific surface and specific connectivity are highly correlated with F1.…”

“…Furthermore, microtomography offers the possibility to extract pore size distribution as well as structural parameters. Among them, pore connectivity, which influences hydrodynamics (Vogel and Roth, 1998), or specific surface (surface area/volume) (Gerke, 2012) can be estimated.…”

Suction Induced Effects on the Fabric of a Structured Soil

“…This implies the consideration of a representative elementary volume (REV) of a given material. A REV is required to include a significant amount of small-scale heterogeneity to respect a meaningful statistical average (Vogel and Roth, 1998). As an example, the dependence of the sample porosity on its scale is shown in Figure 1.…”

Insights into the Relationships Among Capillary Pressure, Saturation, Interfacial Area and Relative Permeability Using Pore-Network Modeling

“…In addition to using pore-network models for theoretical studies, some researchers have tried to develop predictive models for various purposes. Vogel (1997Vogel ( , 2000, and Vogel and Roth (1998) used the serial sectioning technique to produce a representative pore-network, and modeled soil relative permeability. Hui and Blunt (2000) have also modeled the relative permeability for a three-phase system using a bundle of tubes of different sizes with constant triangular cross sections.…”