Saturated Hydraulic Conductivity of Surface Seals Estimated from Computed Tomography-Measured Porosity

고해상도 X-ray CT 를 이용한 토양표면 피막의 공극율 및 포화수리전도도 측정

  • Lee, Sang-Soo (Dep. of Biological Environment, Kangwon National University) ;
  • Gantzer, C.J. (Dep. of Soil, Environmental and Atmospheric Sciences, University of Missouri) ;
  • Thompson, A.L. (Dep. of Biological Engineering, University of Missouri) ;
  • Anderson, S.H. (Dep. of Soil, Environmental and Atmospheric Sciences, University of Missouri) ;
  • Ketchum, R.A. (Dep. of Geological Sciences, University of Texas) ;
  • Ok, Yong-Sik (Dep. of Biological Environment, Kangwon National University)
  • 이상수 (강원대학교 바이오자원환경학과) ;
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  • 옥용식 (강원대학교 바이오자원환경학과)
  • Published : 2011.07.01

Abstract

Relationships between soil saturated hydraulic conductivity ($K_s$) and porosity (${\phi}$) have been developed over many years; however, use of these relationships for evaluating rain-induced seals is limited mainly because of difficulties in estimating seal pore-size characteristics. The objectives of this study were to evaluate the $K_s$ of soil surface seals over a range of thicknesses, where seal thickness was determined using a High-Resolution-Computed-Tomography (HRCT) scanner, and to investigate relationships between $K_s$ and ${\phi}$ of developing seals in samples with equivalent diameters (e.d.) ${\geq}15\;{\mu}m$. A Mexico silt loam soil was packed to a bulk density (${\rho}_b$) of $1.1\;Mg\;m^{-3}$ in cylinders 160-mm i.d. by 160-mm long and subjected to $61-mm\;h^{-1}$ simulated rainfall having a kinetic energy (KE) of $25\;J\;m^{-2}\;min^{-1}$ for 7.5, 15, 30, and 60 min to create a range in seal development. Thicknesses of the seal layers were determined by analysis of HRCT images of seals. The $K_s$ values of the seals were estimated using an effective $K_s$ value ($K_{s-eff}$). The $K_s-{\phi}$ relationship was described by a Kozeny and Carmen equation, $K_s=B{\phi}^n$; where B and n are empirical constants and n = 31. This approach explained 86% of the variation between $K_s$ and ${\phi}$ within the soil seals. Knowledge of surface seal information and hydraulic conductivity can provide useful information to use in management of sites prone to sealing formation.

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