Particle size distribution, also known as gradation, refers to the proportions by dry mass of a soil distributed over specified particle-size ranges. Gradation is used to classify soils for engineering and agricultural purposes, since particle size influences how fast or slow water or other fluid moves through a soil. Two proposed new ASTM standards provide test methods for determining particle size.
WK11776, Test Methods for Determining Particle Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis, and ASTM WK38106, Test Method for Particle Size Analysis of Soils Conbining the Sieve and Sedimentation Techniques, are being developed by Subcommittee D18.03 on Texture, Plasticity and Density Characteristics of Soils, part of ASTM Committee D18 on Soil and Rock.
“Knowing the grain size distribution of a soil is important for a variety of reasons and for a range of uses,” says Kendra Adams, senior quality assurance engineer, Fugro Consultants Inc., and a D18 member. “Gradation results influence the design of earthen dams, levees and landfills.”
Once approved, the proposed standards will be used by professionals in several fields:
- Civil and geotechnical engineers will use information gained from use of the standards to assist them in designing or making recommendations regarding a project site, particularly regarding water drainage;
- Geologists will find WK11776 helpful in determining depositional environments and provenance;
- Agronomists will use the method to assist with drainage or nutrient delivery to crops;
- Regulatory and accreditation bodies will have a consistent and accepted method by which to assess laboratories; and
- Laboratories will have a defined method by which to perform the test.
D18.03 welcomes participation in its standards developing activities from all interested parties.