THE ACCURACY OF HYDROMETER ANALYSIS FOR FINE-GRAINED CLAY PARTICLES

The Standard Test Method for Particle-Size Analysis (ASTM D422-63) relies on the well-known Stokes' equation for estimating particle diameters. The validity of Stokes' equation for fine-grained particle size analysis is based on assumptions, including the assumption that actual particle shapes can be approximated by smooth spheres. This paper provides a rigorous analysis of the accuracy of Stokes' equation for calculating particle-size distributions of nonspherical, fine-grained clay particles. Analytical expressions relating the actual particle shape and size to the equivalent "Stokes' diameter" are presented for disk-shaped and rod-shaped particles. Disks and rods are chosen to represent the high aspect ratios typically exhibited by real clay particles. For particle sizes ranging from 0.1 to 100 microns and for aspect ratios ranging from 10 to 500, it is shown that Stokes' equation underestimates the maximum particle dimension by up to two orders of magnitude. Consequently, particle-size distributions calculated from conventional hydrometer analysis are shown to be misleading. To confirm the contention that Stokes' equation may not be appropriate for calculating particle sizes and particle-size distributions for fine-grained clays, kaolinite and pulverized mica are characterized by comparing results from hydrometer analysis, sieve analysis, laser diffraction analysis, and scanning electron microscopy (SEM). The experimental results confirm the error estimates from the theoretical evaluation.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/01496115
• Corporate Authors:

  American Society for Testing and Materials (ASTM)

  100 Barr Harbor Drive, P.O. Box C700
  West Conshohocken, PA  United States  19428-2957
• Authors:
  • Lu, Ning
  • Ristow, Gerald H
  • Likos, William J
• Publication Date: 2000-12

Language

• English

Media Info

• Features: Figures; References;
• Pagination: p. 487-495
• Serial:
  • Geotechnical Testing Journal
  • Volume: 23
  • Issue Number: 4
  • Publisher: ASTM International
  • ISSN: 0149-6115
  • EISSN: 1945-7545
  • Serial URL: https://www.astm.org/products-services/standards-and-publications/geotechnical-testing-journal.html

Subject/Index Terms

• TRT Terms: Accuracy; Clay; Diameter; Electron microscopy; Fine grained soils; Grain shape (Geology); Grain size (Geology); Hydrometers; Kaolinite; Mica; Sedimentation; Sieve analysis; Sizing apparatus; Soil particles
• Uncontrolled Terms: Laser diffraction; Stokes equation
• Subject Areas: Geotechnology; Highways; I42: Soil Mechanics;

Filing Info

• Accession Number: 00805800
• Record Type: Publication
• Files: TRIS
• Created Date: Feb 11 2001 12:00AM