Index properties of soil
- 1. INDEX PROPERTIES OF SOIL
- 2. INDEX PROPERTIES OF SOIL The tests required for determination of engineering properties (permeability, shear strength, compressibility etc.) The properties of soils which are indicative of engineering properties are called index properties. Moreover, proper classification and identification of the soils of interest would rather become very expensive without the aid of index properties.
- 3. The main index properties of coarse-grained soils are particle size distribution and the relative density. For fine-grained soils, the main index properties are consistency and consistency limits or Atterberg’s limits. Moisture content, void ratio, porosity, degree of saturation etc. are useful index properties of soils
- 4. SOIL GRADATION OR SOIL PARTICLE SIZE DISTRIBUTION Soil gradation or soil particle size distribution is by mechanical analysis, also known as particle size analysis. It is a method of separation of soils into different fractions based on the particle size. It expresses quantitatively the proportions, by mass, of various sizes of particles present in a soil. It is shown graphically on a particle size distribution curve The mechanical analysis is done in two stages: (i) Sieve Analysis, (ii) Sedimentation Analysis. Sieve Analysis is used for coarse-grained soils (particle sizes greater than 0.075 mm) which can easily pass through a set of sieves (particle sizes smaller than 0.075mm).
- 5. (I) SIEVE ANALYSIS: The soil is sieved through a set of sieve. Sieves are generally made of spun brass and phosphor branz (stainless steel) sieve cloth. Sieves of various sizes ranging from 75 mm to 0.075 mm (# 200) are available. As mentioned before, the sieve analysis is done for coarse-grained soils. The coarse-grained soils can be further subdivided into gravel fraction (size > 4.75 mm) and sand fraction (0.075 mm or # 200 < size 4.75 mm or # 4). A set of sieves consisting of the sizes shown in the following figure can be used for sands.......
- 8. PARTICLE SIZE DISTRIBUTION CURVE (EXAMPLE) The particle size distribution curve, also known as a gradation curve, represents the distribution of particles of different sizes in the soil mass. The percentage finer than a given size is plotted as ordinate (on natural scale) and the particle size as abscissa (on log scale)
- 10. Where, D30 = particle size corresponding to 30 % finer For sands..... If Cu > 6 and 1 CC 3 ------------------------- The soil is well-graded. otherwise, poorly-graded For Gravel...... If Cu > 4 and 1 CC 3 ------------------------- The soil is well-graded. otherwise, poorly-graded
- 11. GRADATION OF SOIL (EXAMPLE) The distribution of particles of different sizes in a soil mass is called grading. The grading of soils can be determined from the particle size distribution curves
- 12. A flat S-curve, such as curve (A) represents a soil which contains a wide range of particles of different sizes in good proportion. Such a soil is called a well-graded soils. A steep curve, like (B), indicates a soil containing the particles of almost the same size. Such soils are known as poorly-graded soils.
- 15. SOL
- 16. EXAMPLE
- 19. EXAMPLE
- 20. Where, D60 = particle size such that 60 % of the soil is finer than this size D10 = particle size such that 10 % of the soil is finer than this size D10 size is also known as effective size. The larger the numerical value of Cu, the more is the range of particles (well-graded)
- 21. CLASS WORK