CHARACTERIZATION OF PREFERENTIAL FLOW PATHS IN COMPACTED SAND-CLAY MIXTURES

The authors performed laboratory soil-column experiments to study the distribution of preferential flow paths resulting from removal of colloidal-size clay particles. An assumption was made that flow paths resulted from fluid energy overcoming the cementitious bonding of particles along the pore walls. These experiments studied specifically the influence of clay percentage in sand-clay mixtures and the effect of hydraulic gradients on pore evolution. Analysis of the effluent during the experiments revealed that clay particles were removed from the soil column, accompanied by an increase in porosity and hydraulic conductivity. Dye was used on the same columns to stain the pathways where colloidal particle removal occurred. The dye experiments indicated that pore distribution was uniform in some cases, but other cases showed distinct preferential flow-path formation. The dye pattern was converted to a binary file, using concepts of image analysis, and analyzed as a spatial random process to characterize the spatial distribution of flow paths. Key parameters to quantify the random dye patterns and to describe the nature of flow-path evolution were the expected spatial density and the correlation length. 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. Soil detachability was another key parameter, which defines the ease with which colloids can be removed from the pore walls. Expected spatial density displayed an identifiable trend with G, while correlation length was largely dependent on detachability of the mixture.

Language

  • English

Media Info

  • Features: Appendices; Figures; References; Tables;
  • Pagination: p. 652-659
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00711518
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Sep 8 1995 12:00AM