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ASTM System
  • Rock Fragments - particles larger than 3 inch seive
  • Soil - Anything Smaller than a 3 inch sieve
  • Fine Soils - anything smaller than 0.075 mm
Sieve Analysis
  • Measures the grain size distribution of soil by passing it through a series of sieves
Clean Sand
Dirt Sand
  • Clean Sand - primarily sand, with less than 5% silt or clay
  • Dirt Sand - more than 5% silt or clay
Hydrometer Analysis
  • Measures the amount of silts and clay that passes through a #200 sieve (0.075 mm)
  • Uses Stokes Law by using the specific gravity of particles
Grain Distribution Curve
  • Plots grain diameter vs. Percentage of solids by weight smaller (Percent finer)
Reading the Distribution Curve
Cuves on the left
curves on the right
poorly graded (uniformely graded)
well graded
  • curves on the left - fine grained soils
  • curves on the right - coase grained
  • poorly graded - curves that are verticle
  • well graded - soils with flat curves contain a wide vareity of particle sizes
Well - Sorted
  • Lots of particle sizes = poorly graded
Poorly Sorted
  • narrow range of particle sizes = well graded
Gap Graded
  • Curves that have nearly flat sections, meaning they are missing particle sizes
D sizes
  • particle diameters that correspond to certain percent passing values for a given soil
Coefficient of Uniformity - Cu
  • steep curves - poorly graded soils - have low values of Cu
  • Flat Curves - well graded soils - have high values of Cu
Coefficient of Curvature
  • Soils with smooth curves have Cc values of 1-3
  • Sils with irregular curves have higher or lower values
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