AIR PERMEABILITY OF POROUS MATERIALS UNDER CONTROLLED LABORATORY CONDITIONS

A series of air permeability tests were conducted on four hand-packed samples of alluvial sands and glass beads using a newly developed air permeameter, The permeameter was tested and found capable of precisely controlling soil-water matric potential (in the range 0 to 1 bar) whi le simultaneously facilitating the direct measurement of air permeabil ity in porous media. Permeameter results indicate that air permeabilit y increases with a corresponding decrease in water content over a mono tonic drainage cycle. It was observed that the rate of change in air p ermeability with respect to changes in water content is highest at hig h water content and lowest at low water content. In several soil sampl es, the air permeability approached a constant value at low water cont ent, Air permeability variations with water content were observed to d iffer among soils of different texture, For example, the intrinsic per meability of water was 11 to 86% of the maximum air permeability, The new permeameter allowed rapid and accurate measurements of air permeab ility in fine-textured materials over a wide range of matric potential s and water content.