Lesson 1/Learning Event 2
To determine the Coefficients of Uniformity and Curvature using the Grain Size Distribution Graph,
follow these procedures:
1. Trace a line from 60 percent on the abscissa to the right until it intersects the curve. Then drop
straight down to find a value of grain size in millimeters on the ordinate. That grain size equals
D60.
2. Trace a line from 30 percent on the abscissa to the right until it intersects the curve. Then drop
straight down to find a value of grain size in millimeters on the ordinate. That grain size equals
D30.
3. Repeat the same steps beginning at 10 percent to determine the value of D10.
Specific Gravity of Soil. The specific gravity, designated by the ratio between the weight per unit
volume of the material at a stated temperature and the weight per unit volume of water at a stated
temperature, usually 20,C. The specific gravity (metric system) equals:
Weight of Sample in Air (gms)
Weight Sample in Air (gms) - Sample Submerged (gms)
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