BE-02 Open cut method Lesson: Installation of Pipes

Physical Characteristics of Soil

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]
Criteria for Assigning Group symbols and Group Names Using Laboratory TestsA
Soil Group Symbol
Soil Group Name
COARSE-GRAINED SOILS
Gravels
Clean Gravels
Cu ≥ 4
and 1≤ Cc ≤ 3C
GW
Well-graded gravelD
More than 50 % retained on No. 200 sieve
More than 50 % of coarse fraction retained on No. 4 sieve
Less than 5 % finesE
Cu < 4 and/or 1 > Cc > 3C
GP
Poorly graded gravelD
 
 
Gravels with Fines
Fines classify as ML or MH
GM
Silty gravelD,F,G
 
 
More than 12 % finesE
Fines classify as CL or CH
GC
Clayey gravel D,F,G
 
Sands
Clean Sands
Cu ≥ 6 and
1≤ Cc ≤ 3C
SW
Well-graded sandH
 
50 % or more of coarse
Less than 5% finesI
Cu < 6 and/or
1 > Cc > 3C
SP
Poorly graded sand
 
fraction passes No. 4 sieve
Sands With Fines
Fines classify as CL or CH
SM
Silty sandF,G,H
 
 
More than 12 % finesI
Fines classify as CL or CH
SC
Clayey sandF,G,H
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.

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