Percolation theory and hydrodynamics of soil-peat mixtures
2000
Vidal-Beaudet, L. | Charpentier, S.
Great quantities of organic matter are added reconstituting soils in urban conditions. To evaluate the efficiency of organic matter on physical properties of reconstituted soils, we studied the effects of loading on intrinsic permeability of soils mixed with peat. Percolation theory associated with a statistical porosity approach was used to explain variation of permeability related to porosity. After compression, sample porosity was measured and the pore-space morphology described by image analysis. An ellipse with major axis (a) and minor axis (b) was inscribed within each pore. All the pores appeared as lenses of different sizes which could be assumed to represent disk-shaped cracks characterized by a diameter d and an aperture e. The crack model was calculated by means of a percolation threshold, Pc = 0.33, along with values d and e as well as the measured porosity. This allowed a determination of the crack interconnection factor f. During compression, the number of pores per unit area decreased. Increasing the loading closed off pores and modified flow pathways. Connected sites facilitating percolation became disconnected from each other and the flow was reduced. The effective porosity, which actually took part in flow, was determined for all the samples and was dependent on peat content.
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