Estimating scale dependence of saturated hydraulic conductivity in soils

Understanding the effect of scale on hydraulic and physical properties of soils has broad applications to scaling problems in hydrogeology, soil physics, and environmental engineering. The scale dependence of flow and transport is attributed to spatial heterogeneities, such as pore-size distribution and pore connectivity at small scales (e.g., core), fracture orientation and long-range correlations at large scales (e.g., field). In this study, we apply concepts from percolation theory to estimate the scale dependence of saturated hydraulic conductivity, K_sat. For this purpose, we use a database including undisturbed soil samples from four Danish sites (Jyndevad, Tylstrup, Estrup, and Silstrup). The value of K_sat was measured at small (100 cm³) and large (6280 cm³) scales. First, we apply a classification approach, widely used in petroleum engineering, to group soils based on their similarities in hydraulic properties using porosity and K_sat measurements at the small scale. We detect nine different soil classes with the average flow zone indicator (FZI) from 0.05 [mu]m in class 1 to 9 [mu]m in class 9. Next, using percolation theory, we characterize the scale dependence of critical pore-throat radius. We use the critical path analysis to link the critical pore-throat radius to K_sat and, consequently, determine the scale dependence of K_sat. Comparing the theoretical estimations with the experimental measurements show that the percolation theoretic model reasonably well estimates the K_sat at the large scale from the soil water retention curve and K_sat measured at the small scale. We find the root mean square log-transformed error (RMSLE) values 0.45, 0.77, 1.9, and 2.05 (cm/day) for sites Jyndevad, Tylstrup, Silstrup, and Estrup, respectively. Results show that the theory tends to provide more accurate estimations in coarser textures and unstructured soils as well as soil classes with FZI values greater than 0.7 [mu]m.

Grantor dc:publisher

Kansas State University

Year dc:date.issued

2022

Author dc:creator

• Kaminski, Skylar Jace

• Soil physics
• Hydrogeology
• Hydraulic conductivity
• Scale

Statement dc:rights

• © the author. This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

https://hdl.handle.net/2097/42869

OAI identifier oai:identifier

oai:krex.k-state.edu:2097/42869