Nondestructive quantification of macropore volume using shear-thinning fluid

Abstract

Understanding and quantifying the role of preferential pathways, such as soil cracks, on flow in porous media requires accurate estimation of their volume and connectivity. Current estimation methods either are based on surface measurements, which cannot account for complex geometries or networks, or are destructive to the system being studied. In this study, we developed a new, nondestructive method that utilizes a known volume of shear-thinning viscous solution (here based on guar gum) to fill preferential pathways, with limited infiltration into the soil matrix. Theoretical expressions were developed to predict the shear-thinning properties of a range of solution concentrations and the amount of solution lost to matrix infiltration. Laboratory and field experiments tested the theory and assessed the utility and accuracy of the proposed method, which was found to be practicable as predicted. © Soil Science Society of America.