classification of soil details aas per is ,us,classification geotechnical engineering

Ge Classification of Soil

1. Problem: An undisturbed saturated specimen of clay has a volume of 18.9 cm 3 and a mass of 30.2 g. On oven drying, the mass reduces to 18 g. The volume of dry specimen as determined by displacement of mercury is 9.9 cm 3 . Determine shrinkage limit, specific gravity, shrinkage ratio and volumetric shrinkage. Solution: M 1 = 30.2g, M d = 18g, ρ w = 1 g/cc V 1 = 18.9 cm3 V 2 = 9.9 cm 3

2. Shrinkage Limit

3. Shrinkage Limit

4. Shrinkage Limit

5. Shrinkage Limit

6. Shrinkage Limit

7. i ) w s = [(M 1 – M d )/ M d ] – [(V 1 – V 2 )x ρ w / M d ] x 100 = [(30.2-18)/18] – [(18.9 – 9.9) x 1/18] x 100 = 17.8% ii) G = M d /(V 1 -(M 1 – M d )) = 18/(18.9 –(30.2- 18)) = 2.69 Alternatively G = 1 /[( ρ w / ρ d ) – ( w s /100)] ρ d = 18/9.9 = 1.818 g/cc ρ w = 1 g/cc From i ), w s = 17.8% G = 2.69

8. iii) SR = ϒ d / ϒ w = ρ d / ρ w = G m = 1.818/1 = 1.82 IV) Volumetric Shrinkage (VS) VS = [(V 1 – V d ) x 100]/ V d = [(18.9 – 9.9) X 100] /9.9 = 91% Alternatively, VS = (w 1 – w s ) SR = (67.8 – 17.8) X 1.82 = 91%

9. Pr 2: The mass specific gravity of a fully saturated specimen of clay having a water content of 36% is 1.86. On oven drying, the mass specific gravity drops to 1.72. Calculate the specific gravity and its shrinkage limit. Solution: e = w sat . G = 0.36 G G m = ϒ sat / ϒ w G m =[[( G+e ) ϒ w ]/(1+e)] X 1/ ϒ w 1.86 = (G+0.36G)/1+0.36G) = 1.36G/(1+0.36G) G= 2.69 From which, w s = ( ϒ w / ϒ d ) – 1/G where ϒ d / ϒ w = 1.72 = mass specific gravity of dry soil w s = [(1/1.72) – (1/2.69)] = 0.21 = 21% Alternatively,

10. Alternatively, e dry = {[(G ϒ w / ϒ d )] -1 } = {[G ρ w / ρ d ] -1} = [[2.69 x 1/1.72] -1] = 0.565 w s = e/G = 0.565/2.69 = 0.21 =21%

11. Soils and their Classification

12. Soils - What are they? Particulate materials - Sedimentary origins (usually) - Residual Wide range of particle sizes - larger particles: quartz, feldspar - very small particles: clay minerals Voids between particles

13. Need for Simple Classification Usually soil on site has to be used. Soils differ from other engineering materials in that one has little control over their properties Extent and properties of the soil have to be determined Cheap and simple tests are required to give an indication of engineering properties, e.g. stiffness, strength, for preliminary design The classification must use core samples obtained from the ground. This information is often supplemented by in-situ tests such as cone penetration tests.

14. Purpo s e

15. Purpo s e Arrange various types of soils into groups according to their engineering or various other characteristics. Soil possessing similar characteristics can be placed in the same group.

16. Soil Classification Systems Particle Size Classification Textural Classification Highway Research Board (HRB) Classification Unified Soil Classification System (USCS) Indian Standard Classification System (ISCS)

17. Particle Size Classification

18. Soils arranged according to grain sizes. Terms such as gravel, sand, silt and clay are used to indicate grain sizes. These terms are used only as designation of particle sizes. They do not signify naturally occurring soil types. Naturally occurring soil are mixture of particles of different sizes. Int r oduction

19. IS Classification of Grain Size

20. Textural Classification

21. Soil classification of composite soils exclusively based on Particle Size Distribution. Most popular is the Triangular Classification of U.S. Public Roads Administration. Classification based on % of sand, silt and clay size. More suitable for describing coarse grained soil. Clay soil properties are less dependent on particle size distribution. Int r oduction

22. Textural Classification Chart

23. E x ample 30% sand 30% silt 40% clay Soil Type Clay

24. Highway Research Board (HRB) Classification

25. Based on both particle-size composition as well as plasticity characteristics. Mostly used for pavement construction . 7 primary groups (A-1, A-2,…., A-7). A-1 subdivided into 2 subgroups. A-2 subdivided into 4 subgroups. Introduction to HRB Classification

26. Used to describe performance of soil when used for pavement construction. Not used to place a soil in a particular group. It means rating the value of soil as a subgrade material within its own group. Higher the value of GI, poorer is the quality of material. Group Index (GI)

27. Group Index of a soil depends on: 1. Amount of material passing 75 micron IS sieve. 2. Liquid Limit. 3. Plastic Limit. Group Index determination

28. Group Index

29. Group Index

30. Proceed from left to right on the chart. Correct group will be found by process of elimination. The first group from left into which the test data will fit will be the correct classification. Group Index should be rounded off to nearest integer and placed in parenthesis, such as, A-2-2 (6).

31. Unified Soil Classification System USCS

32. Origin of USCS First developed by Professor A. Casagrande (1948) for the purpose of airfield construction during World War II. Afterwards, it was modified to enable the system to be applicable to dams, foundations, and other construction .

33. Four Major Divisions Course G r ained Fine G r ained O r ganic Soil Peat

34. Classification Groups The soil is classified into 15 groups . Each group is designated a symbol consisting of two capital letters. The first letter is based on main soil type. The second letter is based on gradation and plasticity .

35. Classification Group Symbols Main Soil Type Prefix Subgroup Suffix Classification Group symbols G r a v el G Well-graded P oo r l y - g r ad e d Silty Clayey W P M C GW GP GM GC Sand S Well-graded P oo r l y - g r ad e d Silty Clayey W P M C SW SP SM SC Silt M LL < 50% LL > 50% L H ML MH Clay C LL < 50% LL > 50% L H CL CH O r g anic O LL < 50% LL > 50% L H OL OH Peat Pt Pt

36. U ni f ie d S o i l Classi f icatio n S y s t em ( C o n t d . )

37. Plasticity Chart Below A-line, use M (Silt) or O (Organic) Above A-line, use C - Clay High Plasticity use H - w L >50 Low Plasticity use L - w L <50 Silt (M) Clay (C) Organic (O)

38. Plasticity Chart “The soil’s liquid limit (w L ) after oven drying is less than 75 % of its liquid limit before oven drying.” If the above statement is true, then it is Organic Soil (OL or OH). Otherwise, it is Inorganic Soil (ML or MH)

39. Plasticity Chart When I P and w L are in the hatched portion of the plasticity chart, the soil is given dual symbol (CL-ML). Soil possessing properties of more than one group are termed as boundary soil and designated by dual group symbol.

40. USCS at a glance + (Santamarina et al., 2001)

41. Group Symbols and Group Names Group Symbol Typical Name GW Well-graded gravels. GP Poorly-graded gravels. GM Silty gravels. GC Clayey gravels SW Well-graded sands. SP Poorly-graded sands. SM Silty sands. SC Clayey sands.

42. Group Symbol Typical Name CL Inorganic clays of low plasticity. ML Inorganic silts with slight plasticity. OL Organic soil of low plasticity. CH Inorganic clays of high plasticity. MH Inorganic silts with high plasticity. OH Organic soil of high plasticity. Pt Peat. Group Symbols and Group Names

43. Group Symbols and Group Names

44. Indian Standard Classification System (ISCS) I S : 1 498-1 97

45. Int r oduction Based on USCS system Modifications are: Fine grained soils subdivided into 3 groups (low, intermediate and high plasticity) as against two groups(low and high) in USCS. w L < 35 = L , 3 5 < W L < 5 =I , w L > 5 0 = H Thus, soil classified into 18 groups as against 15 in USCS.

46. Classification Group Symbols Main Soil Type Prefix Subgroup Suffix Classification Group symbols G r a v el G Well-graded P oo r l y - g r ad e d Silty Clayey W P M C GW GP GM GC Sand S Well-graded P oo r l y - g r ad e d Silty Clayey W P M C SW SP SM SC Silt M LL < 35% 3 5 < LL< > 50 LL > 50% L I H ML MI MH Clay C LL < 35% 3 5 < LL< > 50 LL > 50% L I H CL CI CH O r g anic O LL < 35% 3 5 < LL< > 50 LL > 50% L I H OL OI OH Peat Pt Pt

47. Plasticity Chart High Plasticity use H - w L >50 Intermediate Plasticity use I – 35< w L >50 Low Plasticity use L - w L <35 Below A-line, use M (Silt) or O (Organic) Above A-line, use C - Clay

48. Grading Curves W - Well graded P – Poorly graded Gap graded

49. Boundary Classification Coarse grained soils: GW –GP, GM-GC, GW-GM, GW_GC, SW-SP, SM-SC, SW-SM, Fine grained soils: ML-MI,CL-CI,MI-MH, CH-OH Coarse and fine grained soils: SM-SL, SC-CL In coarse grained soils, if fines between 5 to 10% and PI between 4 to 7soils can be represented as GM &GC or SC such cases Non Plastic classification is favoured

50. Problem: Sketch the plasticity chart used for classifying fine grained soil in the IS soil classification system. Give the group symbols for the following soils Liquid limit = 40% Plastic limit = 22% Liquid limit = 20% Plastic limit = 14% Passing 4.75 mm sieve = 70%, Passing 75 µ sieve = 8% Cu = 7, Cc = 3, PI = 3

51. Solution Liquid limit = 40% Plastic limit = 22% PI = WL – Wp = 40 – 22 = 18% WL = 40% and PI = 18%, from the Plasticity chart Group symbol = CI

52. ii) Liquid limit = 20% Plastic limit = 14% PI = WL – Wp = 20 – 14 = 6% WL = 20% and PI = 6%, from the Plasticity chart Group symbol = CL-ML

53. iii) Since greater than 70% is passing through 4.75 mm sieve, the soil is Sandy (S) Cu = 7 i.e >6 and Cc = 3, hence soil is SW But % passing through 75 µ sieve is 8% (b/w 5 to 12%) It is a boarder line case. Also, PI = 3, (<4) it satisfy the requirement of SM. Hence the soil is designated as SW-SM

54. Hydrometer Analysis https://www.youtube.com/watch?v=GfDW3Fw9cL0

55. Thank You Reference from internet and text books