Determination grain size distribution of soil

SOIL MECHANICS LAB

1. DETERMINATION OF GRAIN SIZE DISTRIBUTION EXPERIMENT NO 5 SOIL MECHANICS LABORATORY CE PC 594

2. DIFFERENT TYPES OF SOIL Particle size means diameter of particle (d) Soil may consists of clay, silt, sand, gravel, cobble and boulder Particle size above than 75µ will be coarse grained soil and particle size below 75µ will be fine grained soil

3. CLASSIFICATION OF SOIL BASED ON PARTICLE SIZE 300 mm 80 mm 75 µ 4.75 mm 2 µ Boulder Cobble Gravel Sand Silt Clay Fine Grained Soil Coarse Grained Soil Note:- µ =  

4. CLASSIFICATION OF SOIL BASED ON PARTICLE SIZE 80 mm 75 µ 4.75 mm Coarse Gravel Medium Sand 20 mm 425 µ 2 mm Fine Gravel Coarse Sand Fine Sand

5. IMPORTANCE OF PARTICLE SIZE DISTRIBUTION Particle size distribution will help you to evaluate Type of soil Gradation of soil

6. GRADATION OF SOIL There are four types of gradation of soil Well graded soil Poorly graded soil Uniformly Graded soil Gap Graded soil

7. GRADATION OF SOIL Well graded soil- If the soil have good representation of all sizes of particle , it is called as well graded soil. Poorly graded soil- If the soil have excess of some sizes of particle and deficiency of another size of particle, it is called as poorly graded soil. Uniformly Graded soil- If the soil have only one size of particle , it is called as uniformly graded soi l . Gap Graded soil- If certain size of particle are missing from the soil, it is termed as gap graded soil.

8. PARTICLE SIZE DISTRIBUTION CURVE IMPORTANT POINTS: The result of particle size analysis is represented in a form of a curve termed as particle size distribution curve In which percentage finer (N) is expressed on Y axis and corresponding size of particle (d in mm) is expressed on X axis on log scale. This particle size distribution curve helps in analyzing type of soil and gradation of soil.

9. PARTICLE SIZE DISTRIBUTION CURVE

10. PARTICLE SIZE DISTRIBUTION CURVE A D C B E

11. PARTICLE SIZE DISTRIBUTION CURVE Following points can be concluded from the particle size distribution curves are- CURVE A – Well graded soil CURVE B- Poorly graded soil or Well graded sand CURVE C- Poorly graded soil or Well graded gravel CURVE D- Gap graded soil CURVE E- Uniformly graded soil Position of curve indicates type of soil Shape of curve indicated gradation of soil

12. PARTICLE SIZE DISTRIBUTION CURVE 10 30 D 10 D 30 D 60

13. PARTICLE SIZE DISTRIBUTION CURVE IMPORTANT:- For coarse grain soil (sand and gravel only) certain size of particle D 10 , D 30 , D 60 have higher significance than other size of particle. As they helps in representing the characteristics of particle size distribution curve in terms of a parameters known as shape factors. D 10 is called effective size of particle D 10 means size of sieve in mm from which 10% are finer or 10% of particles are finer than D mm sieve size.

14. IMPORTANT TERMS RELATED TO PARTICLE SIZE DISTRIBUTION CURVE Coefficient of Uniformity (C u ) It represents the particle size range of distribution curve along with gradation of soil. NOTE: C u 1, for uniformly graded soil C u >6, for well graded sand C u >4, for well graded gravel.  

15. IMPORTANT TERMS RELATED TO PARTICLE SIZE DISTRIBUTION CURVE Coefficient of Curvature (C c ) It represents the shape of particle size distribution curve. NOTE: If C C is lies in between 1 to 3 - Well graded If C C <1 and C C >3 – Poorly graded A soil will be well graded sand when C u > 6 and 1< C C <3 A soil will be well graded gravel when C u > 4 and 1< C C <3  

16. IMPORTANT TERMS RELATED TO PARTICLE SIZE DISTRIBUTION CURVE PERCENTAGE FINENESS Percentage of particles passing through 75µ sieve, are termed as percentage fineness NOTE : Based on percentage fineness coarse grain soil can be classified If % fineness <5%, then GW, GP, SW & SP can be found. If % fineness >12%, then GM, GC, GM-GC, SM, SC & SM-SC can be found from plasticity chart. If % fineness in between 5% to 12 %, then Gravel and sand can be classified both using gradation and plasticity chart.

17. CLASSIFICATION OF COARSE GRAINED SOIL NOTATION: GW- Well graded Gravel GP- Poorly grade Gravel SW- Well graded Sand SP- Poorly graded sand GM- Silty gravel GC- Clayey gravel GM-GC- Gravel with same silt and clay SM- Silty Sand SC- Clayey Sand SM-SC- Sand with same clay and silt

18. CLASSIFICATION OF FINE GRAINED SOIL

19. CLASSIFICATION OF FINE GRAINED SOIL NOTATION: CH- High compressible Clay (Above A line and w L >60%) CI- Intermediate compressible Clay ( Above A line and 30%< w L <60%) CL- Low compressible Clay ( Above A line and w L <30%) MH- High compressible Silt (Below A line and w L >60 %) MI- Intermediate compressible Silt (Below A line and 30%< w L <60 %) ML- Low compressible Silt (Below A line and w L <30%) O – Organic w L = Liquid Limit

20. TESTS REQUIRED FOR PARTICLE SIZE DISTRIBUTION SIEVE ANALYSIS (For coarse Grained soil) Gravel sieving Sand Sieving Dry sieving Wet sieving SEDIMENTATION ANALYSIS (For fine grained soil) Pipette method Hydrometer method

21. SIEVE The sieves are designated as either by its size (mm or µ) or by its number. According to IS: 460-1962, sieves should be designated by its square openings. Sieve number represents the number of square openings per inch length. EX:- IS SIEVE NO. 10- there is 10 square openings in 1 inch length of sieve, hence greater the sieve number, smaller will be sieve openings.

22. GRAVEL SIEVEING Gravel sieving is done for the soil fraction having size greater than 4.75 mm or the soil which retained over 4.75 mm sieve. Apparatus required: IS SIEVE (300 mm, 80 mm, 40 mm, 20 mm, 10 mm, 4.75 mm) Sieve shaker Balance of 0.1 g sensitivity, along with weights and weight box Brush

23. SAND SIEVEING Sand sieving is done for the soil which passes through 4.75 mm sieve but retained over 75 µ sieve. Apparatus required: IS SIEVE ( 2.36 mm , 1.18 mm, 600 micron, 425 micron, 300 micron, 150 micron, and 75 micron ) Sieve shaker Balance of 0.1 g sensitivity, along with weights and weight box Brush

24. SIEVE ANALYSIS PROCEDURE: Weight accurately about 200gms of oven dried soil sample. If the soil has a large fraction greater than 4.75mm size, then greater quantity of soil, that is, about 5.0 Kg should be taken. For soil containing some particle greater than 4.75 mm size, the weight of the soil sample should be taken as 0.5 Kg to 1.0 Kg. Clean the sieves and pan with brush and weigh them up to 0.1 gm accuracy M 1. Arrange the first set sieves of size 300 mm, 80mm, 40mm, 20mm, 10mm, 4.75 mm and the second set sieves of sizes 2.36 mm, 1.18 mm, 600 micron, 425 micron, 150 micron, 75 micron and pan in a order from top to bottom.

25. SIEVE ANALYSIS PROCEDURE: Keep the required quantity of soil sample on the top sieve and shake it with mechanical sieve shaker for about 5 to 10 minutes. Care should be taken to tightly fit the lid cover on the top sieve. After shaking the soil on the sieve shaker, weigh the each sieve with the soil retained over it (M 2 ). Weight of the soil retained over it will be (Weight of retained soil + Weight of sieve) – Weight of empty sieve i.e. M 2 -M 1

26. SIEVE SIZE in mm (a) Wt of sieve (M 1 ) in gm. (b) Wt of soil+ sieve (M 2 ) in gm. (c) Wt of soil retained ( M 2 -M 1 ) in gm. (d) Percentage wt retained (e) % Cumulative wt retained (f) % finer (N) (g) = 100 – (f) 80 884 891.5 7.5 1.36 1.36 98.64 40 845.5 856 10.5 1.91 3.27 96.73 20 824 839 15 2.72 5.99 94.01 10 794.5 811.5 17 3.09 9.08 90.92 4.75 765.5 786.5 21 3.82 12.9 87.1 2.36 738.5 764.5 26 4.73 17.63 82.37 1.18 672 716.5 44.5 8.09 25.72 74.28 0.6 602.5 649 46.5 8.45 34.17 65.83 0.425 572 684 112 20.36 54.53 45.47 0.3 554.5 701.5 147 26.73 81.26 18.74 0.15 523.5 585.5 62 11.27 92.53 7.47 0.075 509.5 530.5 21 3.82 96.35 3.65 pan 485 505 20 3.64 99.99 0.01 Total 550 SIEVE SIZE in mm (a) Wt of sieve (M 1 ) in gm. (b) Wt of soil+ sieve (M 2 ) in gm. (c) Wt of soil retained ( M 2 -M 1 ) in gm. (d) % Cumulative wt retained (f) % finer (N) (g) = 100 – (f) 80 884 891.5 7.5 1.36 1.36 98.64 40 845.5 856 10.5 1.91 3.27 96.73 20 824 839 15 2.72 5.99 94.01 10 794.5 811.5 17 3.09 9.08 90.92 4.75 765.5 786.5 21 3.82 12.9 87.1 2.36 738.5 764.5 26 4.73 17.63 82.37 1.18 672 716.5 44.5 8.09 25.72 74.28 0.6 602.5 649 46.5 8.45 34.17 65.83 0.425 572 684 112 20.36 54.53 45.47 0.3 554.5 701.5 147 26.73 81.26 18.74 0.15 523.5 585.5 62 11.27 92.53 7.47 0.075 509.5 530.5 21 3.82 96.35 3.65 pan 485 505 20 3.64 99.99 0.01 Total 550

27. SAND SIEVEING Dry sieve is performed for cohesion less soils if percentage fineness are less than 5%. Wet sieve analysis is carried out if percentage fineness are more than 5% and of cohesive nature.

28. WET SIEVEING If silt and clay is present in the sand then wet sieving is adopted in which sand are washed so that fine particles are removed. In wet sieving for washing of silt and clay 2 gm sodium hexa-metaphosphate is used in 1 liter of pure water. Sodium hexa-metaphosphate work as deflocculating agent. Procedure is same as coarse sieving.

29. PRECAUTIONS During shaking the lid on the topmost sieve should be kept tight to prevent escape of soils . While drying the soil, the temperature of the oven should not be more than 105° C because higher temperature may cause some permanent change in the 75 fraction.

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