Equipment for Subsampling and Packing Fragmented Soil Samples for Air and Water Permeability Tests

The permeability ratio, air to water, is used as a measure of the stability of soil structure. Equipment and procedures are described for subsampling, placement in containers, and packing fragmented soil samples for air and water permeability tests. Dropping the soil sample through a 4.75 mm. dia. round‐hole screen into the soil container was found to give a more uniform pack than four other packing methods tested. A reproducible degree of packing, as determined by air permeability determinations, was obtained by dropping the soil‐filled container repeatedly from a height of 2.5 cm. Intrinsic (air) permeability decreased rapidly with degree of soil packing and reached an approximately constant value at about 200 impacts. The relationship between air permeability and bulk density was found to be approximately linear for two soils tested.