The document discusses soil classification systems. It describes the Unified Soil Classification System developed by Casagrande in 1942 for the U.S. Army Corps of Engineers. The system classifies soils based on their grain size distribution and plasticity characteristics. A plasticity chart is shown to classify soils based on their liquid limit and plastic limit values. Two problems are then presented asking to classify soils using the AASHTO and Unified systems based on provided grain size distribution and Atterberg limits data.

1. Chapter IV
SOIL CLASSIFICATION

2. HAWASSA UNIVERSITY FACULTY OF TECHNOLOGY CIVIL ENGINEERING DEPARTMENT
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SOIL MECHANICS- I CHAPTER-IV SOIL CLASSIFICATION 2008-09 MU JAGADEESHA

3. HAWASSA UNIVERSITY FACULTY OF TECHNOLOGY CIVIL ENGINEERING DEPARTMENT
Unified Soil Classification System
The original form of the soil classification system was proposed by Casagrande in 1942 during World War II
for use in air field construction undertaken by the Army Corps Engineers. In co operation with U.S Bureau
of reclamation, the corps revised this system in 1952. At present, it is widely used by engineers (ASTM
designation D-2487). In order to use the classification system, the following points must be kept in mind:
1. The classification is based on material passing a 75 mm (3 in.) sieve.
2. Coarse fraction = percent retained above no. 200 sieve = 100- F200 =R200.
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SOIL MECHANICS- I CHAPTER-IV SOIL CLASSIFICATION 2008-09 MU JAGADEESHA

4. HAWASSA UNIVERSITY FACULTY OF TECHNOLOGY CIVIL ENGINEERING DEPARTMENT
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SOIL MECHANICS- I CHAPTER-IV SOIL CLASSIFICATION 2008-09 MU JAGADEESHA

5. HAWASSA UNIVERSITY FACULTY OF TECHNOLOGY CIVIL ENGINEERING DEPARTMENT
Plasticity chart
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SOIL MECHANICS- I CHAPTER-IV SOIL CLASSIFICATION 2008-09 MU JAGADEESHA

6. HAWASSA UNIVERSITY FACULTY OF TECHNOLOGY CIVIL ENGINEERING DEPARTMENT
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SOIL MECHANICS- I CHAPTER-IV SOIL CLASSIFICATION 2008-09 MU JAGADEESHA

7. HAWASSA UNIVERSITY FACULTY OF TECHNOLOGY CIVIL ENGINEERING DEPARTMENT
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SOIL MECHANICS- I CHAPTER-IV SOIL CLASSIFICATION 2008-09 MU JAGADEESHA

8. HAWASSA UNIVERSITY FACULTY OF TECHNOLOGY CIVIL ENGINEERING DEPARTMENT
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SOIL MECHANICS- I CHAPTER-IV SOIL CLASSIFICATION 2008-09 MU JAGADEESHA

9. HAWASSA UNIVERSITY FACULTY OF TECHNOLOGY CIVIL ENGINEERING DEPARTMENT
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SOIL MECHANICS- I CHAPTER-IV SOIL CLASSIFICATION 2008-09 MU JAGADEESHA

10. HAWASSA UNIVERSITY FACULTY OF TECHNOLOGY CIVIL ENGINEERING DEPARTMENT
Problems
1. The sieve analysis of ten soils and the liquid and plastic limits of the fraction passing through the
No. 40 sieve are given below. Classify the soils by the AASHTO classification system and give the
group indexes.
Sieve Analysis, % Finer
Soil No. No.10 No.40 No.200 Liquid Limit Plastic Limit
1 98 80 50 38 29
2 100 92 80 56 23
3 100 88 65 37 22
4 85 55 45 28 20
5 92 75 62 43 28
6 97 60 30 25 16
7 100 55 08 - NP
8 94 80 63 40 21
9 83 48 20 20 15
10 100 92 86 70 38
2. Classify the following soils by the Unified classification system.
Sieve Analysis, % Finer
Soil No. No.4 No.200 Liquid Limit Plasticity Index
A 92 48 30 08
B 60 40 26 04
C 99 76 60 32
D 90 60 41 12
E 80 35 24 02
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SOIL MECHANICS- I CHAPTER-IV SOIL CLASSIFICATION 2008-09 MU JAGADEESHA