BE-02 Open cut method Lesson: Installation of Pipes

Physical Characteristics of Soil

Cohesive Soil Classification

The following table presents classification of cohesive soils for engineering purposes based on particle size, coefficient of uniformity (Cu) and coefficient of curvature (Cc) [ASTM D2487-06]. Cohesive soils do not crumble, are hard to break up when dry and include clayey silts, sandy clays, silty clays, and clays.

Table: 

Cohesive soil classification table as per [ASTM D2487-06]
Criteria for Assigning Group symbols and Group Names Using Laboratory TestsA
Soil Group Symbol
Soil Group Name
FINE-GRAINED SOILS
Silts and Clays
Inorganic
PI > 7 and plots on or above "A" lineJ
CL
Lean clayK,L,M
50 % or more passes the No. 200 sieve
Liquid limit less than 50
 
PI < 4 or plots below "A" lineJ
ML
SiltK,L,M
 
 
Organic
Liquid limit - oven dried < 0.75
OL
Organic clayK,L,M,N
 
 
 
Liquid limit - not dried
OL
Organic siltK,L,M,O
 
Silts and Clays
Inorganic
PI plots on or above "A" line
CH
Fat clayK,L,M
 
Liquid limit 50 or more
 
PI plots below "A" line
MH
Elastic siltK,L,M
 
 
Organic
Liquid limit - oven dried < 0.75
OH
Organic clayK,L,M,P
 
 
 
Liquid limit - not dried
 
Organic siltK,L,M,Q
ABased on the material passing the 3-in. (75-mm) sieve
JIf Atterberg limits plot in hatched area, soil is a CL-ML, silty clay.
KIf soil contains 15 to 29 % plus No. 200, add "with sand" or "with gravel", whichever is predominant.
LIf soil contains ≥ 30 % plus No. 200, predominantly sand, add "sand" to group name.
MIf soil contains ≥ 30 % plus No. 200, predominantly gravel, add "gravelly" to group name.
NPI ≥ 4 and plots on or above "A" line
OPI < 4 or plots below "A" line
PPI plots on or above "A" line
QPI plots below "A" line

 

 

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