Organic Fine-Grained Soil Classification
Organic fine-grained soils have a 50% or more passing rate through a No.200 sieve. Organic clays and organic silts are soils that would be classified as clay or silt, except that their liquid limit values after oven drying is less than 75 % of their liquid limit value before oven drying [ASTM D2487-06].
The table below presents a classification of organic fine-grained soils (OL and OH).
Table:
Classification of organic fine-grained soil (50% or more passes No.200 sieve) as per [ASTM D2487-06]
|
Group Symbol
|
Plasticity Index
|
% Pass
|
% Sand vs. % Gravel
|
Group Name
|
|
|
OL
|
PI ≥ 4 and plots on or above "A"-line
|
< 30 % plus No.200
|
< 15% plus No.200
|
|
Organic Clay
|
|
15-29% plus No.200
|
% sand ≥ % gravel
|
Organic Clay with Sand
|
|||
|
% sand < % gravel
|
Organic Clay with Gravel
|
||||
|
≥ 30 % plus No. 200
|
% sand ≥ % gravel
|
< 15 % gravel
|
Sandy Organic clay
|
||
|
≥ 15 % gravel
|
Sandy Organic Clay with Gravel
|
||||
|
% sand < % gravel
|
< 15 % sand
|
Gravelly Organic Clay
|
|||
|
≥ 15 % sand
|
Gravelly Organic Clay with Sand
|
||||
|
PI < 4 or plots below "A"-line
|
< 30 % plus No. 200
|
< 15 % plus No. 200
|
|
Organic Silt
|
|
|
15-29% plus No.200
|
% sand ≥ % gravel
|
Organic Silt with Sand
|
|||
|
% sand < % gravel
|
Organic Silt with Gravel
|
||||
|
≥ 30 % plus No. 200
|
% sand ≥ % gravel
|
< 15 % gravel
|
Sandy Organic Silt
|
||
|
≥ 15 % gravel
|
Sandy Organic Silt with Gravel
|
||||
|
% sand < % gravel
|
< 15 % sand
|
Gravelly Organic Silt
|
|||
|
≥ 15 % sand
|
Gravelly Organic Silt with Sand
|
||||
|
OH
|
Plots on or above "A"-line
|
< 30 % plus No. 200
|
< 15 % plus No. 200
|
|
Organic Clay
|
|
15-29% plus No.200
|
% sand ≥ % gravel
|
Organic Clay with Sand
|
|||
|
% sand < % gravel
|
Organic Clay with Gravel
|
||||
|
≥ 30 % plus No. 200
|
% sand ≥ % gravel
|
< 15 % gravel
|
Sandy Organic clay
|
||
|
≥ 15 % gravel
|
Sandy Organic Clay with Gravel
|
||||
|
% sand < % gravel
|
< 15 % sand
|
Gravelly Organic Clay
|
|||
|
≥ 15 % sand
|
Gravelly Organic Clay with Sand
|
||||
|
Plots below "A"-line
|
< 30 % plus No. 200
|
< 15 % plus No. 200
|
|
Organic Silt
|
|
|
15-29% plus No.200
|
% sand ≥ % gravel
|
Organic Silt with Sand
|
|||
|
% sand < % gravel
|
Organic Silt with Gravel
|
||||
|
≥ 30 % plus No. 200
|
% sand ≥ % gravel
|
< 15 % gravel
|
Sandy Organic Silt
|
||
|
≥ 15 % gravel
|
Sandy Organic Silt with Gravel
|
||||
|
% sand < % gravel
|
< 15 % sand
|
Gravelly Organic Silt
|
|||
|
≥ 15 % sand
|
Gravelly Organic Silt with Sand
|
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