Page 301 - Planning and Design of Airports

Make visual examination of soil to determine whether its highly organic, coarse grained, or fine grained. In border-line cases determine amount passing No. 200 sieve Fine grained more than 50% pass No. 200 sieve. Run LL and PL on minus 40 sieve material H L Greater percentage of coarse fraction Liquid limit great

50% or less pass No. 200 sieve.
Run sieve analysis
Coarse grained

Sand (S) percentage of coarse pass No. 4 sieve Less than 5% pass No. 200 sieve ∗ Examine grain-size curve Above “A” line Poorly Well and hatched graded graded zone on plasticity chart SP SW GC Note: Sieve sizes are U.S. Standard.

More than 12% pass No. 200 sieve Run LL and PL on minus No. 40 sieve fraction Limits plot in hatched zone on plasticity chart GM–GC Flowchart for the unified soil classification system.

Highly organic soils (Pt) Fibrous texture, color, odor, very high moisture content, particles of vegetable matter. (stick, leaves, etc.) Gravel (G) Great percentage of course fraction retained on No. 4 sieve Between 5% and 12% pass No. 200 sieve Borderline, to have double symbol approp- riate to gradi

Less than 5% pass No. 200 sieve ∗ Examine grain-size curve Poorly Well graded graded GP GW FIGURE 7-2

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