The relationship between structure and the hydraulic conductivity of soil

Crawford, J.W. (1994) The relationship between structure and the hydraulic conductivity of soil. European Journal of Soil Science, 45(4), pp. 493-502. (doi: 10.1111/j.1365-2389.1994.tb00535.x)

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A random fractal matrix comprising a hierarchical aggregation of primary structural elements is used to capture the characteristics of a heterogeneous soil structure with a tortuous pore space. The influence of heterogeneity of both the solid matrix and the pore space, as well as the shape of the pore boundary, on the saturated and unsaturated hydraulic conductivity is studied. For such random structures, the fractal (Hausdorff) dimension alone is not enough to characterize the structure from the point of view of fluid flow and additional characterizations are introduced. The porosity, ρp, of the primary elements has a critical value, ρc. With probability 1, both the saturated and unsaturated conductivities are found to be dependent as a power law on the length scale, L, at which the measurement is made when ρp>ρc. When ρp<ρc, only the unsaturated conductivity is scaling in length scale, while the saturated conductivity becomes dominated, with probability close to 1, by the conductivity of the largest connecting pores in the structure, i.e. preferential pathways. The relationships between the parameters of the power laws and structure are derived and are found to depend on the fractal (Hausdorff) and spectral dimensions of the solid matrix, denoted dm and inline image respectively. A discussion of the importance of these results for the interpretation and extrapolation of measurements is presented, and the implications for variability and predictability of the hydraulic properties of soil is discussed.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Crawford, Professor John
Authors: Crawford, J.W.
College/School:College of Social Sciences > Adam Smith Business School > Management
Journal Name:European Journal of Soil Science
ISSN (Online):1365-2389

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