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This article in SSSAJ

  1. Vol. 55 No. 5, p. 1231-1238
     
    Received: Feb 12, 1990


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doi:10.2136/sssaj1991.03615995005500050006x

Fractal Fragmentation, Soil Porosity, and Soil Water Properties: I. Theory

  1. Michel Rieu  and
  2. Garrison Sposito
  1. Centre ORSTOM Bondy, 70-74 Route d'Aulnay, 93143 Bondy Cédex, France
    Dep. of Soil Science, Univ. of California, Berkeley, CA 94720

Abstract

Abstract

Recent efforts to characterize soil water properties in terms of porosity and particle-size distribution have turned to the possibility that a fractal representation of soil structure may be especially apt. In this paper, we develop a fully self-consistent fractal model of aggregate and pore-space properties for structured soils. The concept underlying the model is the representation of a soil as a fragmented fractal porous medium. This concept involves four essential components: the mathematical partitioning of a bulk soil volume into self-similar pore- and aggregate-size classes, each of which is identified with a successive fragmentation step; the definition of a uniform probability for incomplete fragmentation in each size class; the definition of fractal dimensions for both completely and incompletely fragmented porous media; and the definition of a domain of length scales across which fractal behavior occurs. Model results include a number of equations that can be tested experimentally: (i) a fractal dimension ≤3; (ii) a decrease in aggregate bulk density (or an increase in porosity) with increasing aggregate size; (iii) a power-law aggregate-size-distribution function; (iv) a water potential that scales as an integer power of a similarity ratio; (v) a power-law expression for the water-retention curve; and (vi) an expression for hydraulic conductivity in terms of the conductivities of single-size arrangements of fractures embedded in a regular fractal network. Future research should provide experimental data with which to evaluate these predictions in detail.

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