The same system with minor modification was adopted by ISI for general engineering purpose (IS 1498 - 1970). This system is based on both grain size and plasticity characteristics of soil. It was adopted with some modification by the U.S. Unified soil classification system was originally developed by Casagrande (1948) and was known as airfield classification system. When the group index value is higher, the quantity of the material is poorer.Ĭlick Here to View AASHTO Classification Chart (iv) Unified Soil Classification System
The group index is defined by the following equation. Soil having fine fractions are further classified based on their group index. A soil is classified by proceeding from left to right on the classification chart to find first the group into which the soil test data will fill. Some of the major groups further divided into subgroups.
In this system the soils are divided into seven major groups. After some revision, this system was adopted by the AASHTO in 1945. This system is developed based on particle size and plasticity characteristics of soil mass. Bureau of Public Roads for the classification of soil for highway subgrade use. It was originally developed in 1920 by the U.S. (iii) AASHTO classification system of SoilĪASHTO classification, (table-2) is otherwise known as PRA classification system. The triangular charts are used to classify soil by this system.įigure – 1 shows the typical textural classification system.įig-1: Textural Classification of U.S. This system specifically names the soil depending on the percentage of sand, silt and clay. The classification of soil exclusively based on particle size and their percentage distribution is known as textural classification system. There are several classification systems fin use, but commonly used systems are shown here. In this system the terms clay, silt, sand and gravel are used to indicate only particle size and not to signify nature of soil type. Grain size classification systems were based on grain size. (i) Grain Size Classification System for Soils
- Indian Standard Classification System for Soilĭifferent Classification of Soils for Engineering Purpose Soil may be broadly classified as follows:.
- (iv) Unified Soil Classification System.
- (iii) AASHTO classification system of Soil.
- (i) Grain Size Classification System for Soils.
- Different Classification of Soils for Engineering Purpose.
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