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Chapter IV SOIL CLASSIFICATION

HAWASSA UNIVERSITY FACULTY OF TECHNOLOGY CIVIL ENGINEERING DEPARTMENT

----------------------------------------------------------------------------------------------------------------------------------- SOIL MECHANICS- I CHAPTER-IV SOIL CLASSIFICATION 2008-09 MU JAGADEESHA

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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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Plasticity chart


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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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