Penetration resistance of fine sandy apedal soils as affected by relative bulk density, water content and texture

The major physical properties that control the penetration resistance of soils are the degree of soil compaction, water content and particle size distribution. Sandy soils with well-sorted particle size distributions and low cohesivity compact and consolidate easily under pressure. Six soil samples with predominantly fine sand fractions and clay contents varying between 8 and 20% silt plus clay were selected to determine the relationships among penetration resistance, relative bulk density and water content. Penetration resistance was measured using a constant-rate penetrometer. The relative bulk density given by the ratio between bulk density and maximum ASTM bulk density was used as the parameter representing the level of compaction. Curves relating penetration resistance to water content at different relative bulk densities and to relative bulk density at different water contents were determined for each soil. All the variables were incorporated into a multiple regression equation. This equation can be used to calculate the penetration resistance of fine sandy apedal soils at specific bulk density, water content and silt- plus-clay content values.