Non-Cohesive Soil Classification
The table below presents the classification of non-cohesive soils for engineering purposes based on particle size, coefficient of uniformity (Cu) and coefficient of curvature (Cc) [ASTM D2487-06].
Table:
Non-cohesive soil classification as per [ASTM D2487-06]
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Criteria for Assigning Group symbols and Group Names Using Laboratory TestsA
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Soil Group Symbol
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Soil Group Name
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COARSE-GRAINED SOILS
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Gravels
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Clean Gravels
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Cu ≥ 4
and 1≤ Cc ≤ 3C
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GW
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Well-graded gravelD
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More than 50 % retained on No. 200 sieve
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More than 50 % of coarse fraction retained on No. 4 sieve
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Less than 5 % finesE
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Cu < 4 and/or 1 > Cc > 3C
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GP
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Poorly graded gravelD
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Gravels with Fines
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Fines classify as ML or MH
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GM
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Silty gravelD,F,G
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More than 12 % finesE
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Fines classify as CL or CH
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GC
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Clayey gravel D,F,G
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Sands
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Clean Sands
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Cu ≥ 6 and
1≤ Cc ≤ 3C
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SW
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Well-graded sandH
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50 % or more of coarse
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Less than 5% finesI
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Cu < 6 and/or
1 > Cc > 3C
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SP
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Poorly graded sand
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fraction passes No. 4 sieve
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Sands With Fines
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Fines classify as CL or CH
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SM
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Silty sandF,G,H
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More than 12 % finesI
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Fines classify as CL or CH
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SC
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Clayey sandF,G,H
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ABased on the material passing the 3-in. (75-mm) sieve
BIf field sample contained cobbles or boulders, or both, add "with cobbles or boulders, or both" to group name.
CCU = D60/D10; CC=(D30)2 / D10 x D60
DIf soil contains ≥ 15 % sand, add "with sand" to group name.
EGravels with 5 to 12 % fines require dual symbols:
GW-GM well-graded gravel with silt
GW-GC well-graded gravel with clay
GP-GM poorly graded gravel with silt
GP-GC poorly graded gravel with clay
FIf fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.
GIf fines are organic, add "with organic fines" to group name.
HIf soil contains ≥ 15 % gravel, add "with gravel" to group name.
