American Society of Civil Engineers

On Conductivity of Soils with Preferential Flow Paths

by R. S. Govindaraju, A.M.ASCE and J. Lin

pp. 1730-1735

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Document type: Conference Proceeding Paper
Part of: North American Water and Environment Congress & Destructive Water
Abstract: Laboratory soil column experiments were conducted to study the distribution of preferential flow paths resulting from removal of colloidal size clay particles. These experiments specifically studied the influence of clay (kaolinite) percentage in sand-clay mixtures and the effect of hydraulic gradients on pore evolution. Analysis of the effluent during the experiments indicated that clay particles were removed from the soil column, accompanied by an increase in porosity and hydraulic conductivity. Dye experiments were conducted on the same columns to stain the pathways where colloidal particle removal occurred. It was observed that pore formation was fairly uniform in some cases, while other cases showed distinct preferential flow path formation. A physically-based model was used to identify a dimensionless parameter, G, which expresses the ratio of detachment and deposition forces at any space-time location. A model, based on equivalent media theory, is proposed to describe the hydraulic conductivity of such soils. Future work will test the theoretical expressions for conductivity with experimental results, and investigate the relationship between G and the equivalent conductivity for such soils

ASCE Subject Headings:
Soil permeability
Hydraulic conductivity
Flow patterns
Laboratory tests
Hydraulic gradients