Unified Soil Classification System (USCS). The fine-grained soils are further divided into the following groups on the basis of the following arbitrarily selected values of liquid limit which is a good index of compressibility. However, from the engineering point of view, the classification may be done with the objective of finding the suitability of the soil for construction of dams, highways or foundations, etc. 2. International soil classification, proposed at the International Soil Congress at Washington. USDA-NRCSii September 2012 FOREWORD Purpose: The following instructions, definitions, concepts, and codes are a field guide for making or reading soil descriptions and sampling soils as presently … These soil particles deformed easily under static load. Image Guidelines 5. Highway Research Board (HRB) classification of soil. Before publishing your articles on this site, please read the following pages: 1. It is also used for the design of drainage filters. The plasticity index of A – 7 – 5 sub-group is equal to or less than liquid limit minus 30. The Highway Research Board (HRB) classification system, also known as Public Road Administration (PRA) classification system, is based on both the particle-size composition as well as the plasticity characteristics. 2. Effect of Shape on Engineering Properties: Practical Significance of Consistency Limits: Determination of Liquid and Plastic Limits Liquid Limit. At least four tests are performed by changing the water content of the sample in such a way that the number of blows required to close the groove lie between 5 to 40 blows. Soil … A ball is formed with about 5 gm of soil paste and rolled into a thread of 3 mm diameter on a glass plate with the fingers of one hand. Soils possessing the characteristics of more than one group are termed as boundary soils and are designated by dual group symbols. Individual solid particle in a soil can have different sizes and this characteristic of soil can have a significant effect on its engineering properties. Soil passing 4.75 mm sieve is used for fine sieve analysis. Indian Standard Soil Classification System, ISCS (IS: 1498-1970). Wet sieving is advisable for soil sample passing through 4.75 mm sieve. There are various grain size classifications in use, but the more commonly used systems are following. Table 3.1 shows the specimen calculation sheet. This classification is based on the percentages of sand, silt and clay Sizes making up the soil. Casagrande tool cuts a groove of 2 mm wide at the bottom, 11 mm wide at the top and 8 mm high. These terms are used only as a designation of particles size and do not signify the naturally occurring soil types, which arc mixtures of particles of different sizes and exhibit definite characteristics. The appropriate descriptive terms are listed in the Tables 3.2 to 3.5. Regarding the clay particle content in soils … A soil sample is said to be well graded if it has all sizes of materials present in it. Coefficient of uniformity, and coefficient of curvature, D10— Particle diameter at which 10% of the soil mass is finer than this size, D30_ Particle diameter at which 30% of the soil mass is finer than. Coarse-grained soils, containing less than 5% fines, are designated by symbols GW and SW if they are well graded and by symbol GP and SP if they are poorly graded. For fine sieve analysis IS: 2.0 mm, 1.0 mm, 600, 425, 300,212, 150 and 75 micron sieves are used. Prepare a part of moist soil having a volume equivalent to a 25 mm cube by adding enough water to make the soil soft but not-sticky. Percentage of soil retained in each sieve is calculated and finally percentage passing through each sieve is obtained. The liquidity index of undisturbed soil varies from less than zero to greater than 1. 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