Laboratory Procedures for Particle Size Analysis

Sep 17, 2024

Particle Size Analysis Laboratory Procedures

Introduction

  • Presented by Dave Whinger from Missouri S&T Geotechnical Labs.
  • Overview of laboratory procedures for particle size analysis.
  • Importance: Helps geotechnical engineers classify soils.

Particle Size Analysis Procedures

1. Mechanical Sieve Analysis

  • Purpose: Determine grain size distribution in coarse grain fraction.
  • Equipment Needed:
    • Stack of sieves (number 4 to 200)
    • Pan and lid
    • Mechanical shaker
    • Digital balance
    • Weighing pull

2. Hydrometer Analysis

  • Purpose: Conducted on fine grain portion (material passing number 200 sieve).
  • Equipment Needed:
    • 1000 ml sedimentation jar
    • 1000 ml control jar
    • ANM 152H hydrometer
    • Soil dispersion device (shake mixer)
    • Sodium hexametaphosphate (dispersion agent)
    • Squirt bottle with water
    • Evaporation dish
    • Rubber stopper
    • Thermometer (Celsius)

Soil Sample

  • Type: L Seal silt from the Mississippi River Valley.
  • Processed: Mechanically pulverized, with added coarse material.

Documentation

  • Lab documents available on Blackboard in PDF format.
  • Relevant ASTM standards:
    • ASTM C136: Sieve analysis of fine and coarse aggregates.
    • ASTM D422: Hydrometer test.

Mechanical Sieve Analysis Procedure

  1. Weigh out 500 g of air-dried soil sample.
  2. Mix sample thoroughly.
  3. Disassemble sieve stack and clean out wedged particles (avoid damaging number 200 sieve).
  4. Pour soil sample into the top sieve and assemble the stack.
  5. Shake in mechanical shaker for 10 minutes.
  6. Weigh the material retained on each sieve and calculate total retained mass (should be within ± 2% of original mass).
  7. Calculate percentage passing by subtracting retained percentages.

Hydrometer Analysis Procedure

  1. Weigh out 60 g of soil from pan (from sieve analysis).
  2. Mix with 125 ml of 4% sodium hexametaphosphate and let stand for 15 minutes.
  3. Calibration:
    • Determine zero correction factor and meniscus correction factor using control jar.
  4. Dispersion:
    • Transfer soil solution to dispersion cup and mix for 2 minutes.
    • Pour into sedimentation jar and fill to 1000 ml mark.
  5. Agitate sedimentation jar for 1 minute.
  6. Take initial hydrometer reading at 2 minutes, then continue readings at 4, 8, 16, 30 minutes, and 1, 2, 4, 8, and 24 hours.
  7. Calculate particle size distribution using hydrometer readings and combine with mechanical sieve data.

Conclusion

  • Combining results from both analyses gives a full grain size distribution of the soil sample.