Soil_Classification_Basics.

1. Soil Classification Basics
Dr. Mohanad Alfach
Ph.D. in Earthquake Geotechnical Engineering

2. Contents
• Soil Classification Systems
• Criteria's of (USCS) soil classification
 Soil Grain Sizes
 Hydrometer analysis
 Soil Plasticity – Atterberg Limits
• AASHTO soil classification
 Classification Steps according to AASHTO
 Group Index (GI) Formula

3. Soil classification usually based on grain size and soil consistency.
Several classification systems exist :
1- Unified Soil Classification System (USCS) according
to (ASTM D2487-11)
2- American Association of State Highway and
Transportation Officials AASHTO according to
(ASTM D3282-09)
3-U.S. Department of Agriculture (USDA).
4- Burmister Soil Identification System.
5-Massachusetts Institute of Technology (MIT)

4. Sieve Analysis
Grain Size Distribution, Cc, Cu
Hydrometer Analysis
Percent Clay
(% < 2mm)
Liquid Limit Plastic Limit
Plasticity Chart
PI
LL
Coarse-Grained
•Gravel
•Sand
Fine-Grained
•Silt
•Clay
Sieve Analysis
Hydrometer Analysis
Liquid Limit
Plastic Limit
Grain Size Distribution, Cc, Cu
Percent Clay
(% < 2mm) Plasticity Chart
PI
LL
Steps of USCS Process

7. Mechanical Sieve Analysis (ASTM D422 , D1140 and AASHTO T88)

8. v
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13. In general….
PI Degree of Plasticity
0 Non plastic
1-5 Slightly plastic
5-10 Low plasticity
10-20 Medium plasticity
20-40 High plasticity
40+ Very high plasticity
(from Burmister, 1949)

16. #200
#40
#10

29. Questions?
Thanks for your time and
attention!