Unified training-part-a


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Unified training-part-a

  1. 1. Unified Soil Classification System Training
  2. 2. Sections of Course <ul><li>Part A - Terms and Definitions </li></ul><ul><li>Part B - USCS using Laboratory Data </li></ul><ul><li>Part C - USCS using Field Techniques </li></ul>
  3. 3. Objectives <ul><li>Define terms important for Unified Soil Classification System </li></ul><ul><ul><li>Percent Fines </li></ul></ul><ul><ul><li>Mechanical Analysis </li></ul></ul><ul><ul><li>Liquid Limit </li></ul></ul><ul><ul><li>Plastic Limit, Plasticity Index </li></ul></ul><ul><ul><li>Water Content </li></ul></ul><ul><ul><li>Organic </li></ul></ul>
  4. 4. Objectives <ul><li>Using supplied laboratory data, correctly classify soils by USCS </li></ul><ul><li>Correctly classify soils in field situations by USCS </li></ul>
  5. 5. Background <ul><li>The Unified Soil Classification System was an outgrowth of the Airfield Classification System </li></ul><ul><li>Grouping is based on engineering properties </li></ul>
  6. 6. USDA Textural Classification <ul><li>USDA Textural System only considers grain size. </li></ul><ul><li>Clay mineralogy and how it affects water holding and plasticity characteristics are not evaluated with this classification system </li></ul>
  7. 7. Engineering Properties <ul><li>Permeability </li></ul><ul><li>Shear Strength </li></ul><ul><li>Consolidation </li></ul><ul><li>Shrink/Swell </li></ul>
  8. 8. Parameters Used in Classification System <ul><li>Particle Size </li></ul><ul><li>Water Holding and Plasticity </li></ul><ul><li>Organic Content </li></ul>
  9. 9. ASTM Standards <ul><li>Lab Data Classification is by ASTM D2487 </li></ul><ul><li>Classification of Peat Samples, see ASTM D 4427 </li></ul><ul><li>Field Classification is by D2488 </li></ul>
  10. 10. Definitions <ul><li>Particle Sizes </li></ul><ul><ul><li>Gradation or Mechanical Analyses </li></ul></ul><ul><ul><li>Sieves for larger particles </li></ul></ul><ul><ul><li>Hydrometer for fine particles </li></ul></ul>
  11. 11. Sieve Analyses
  12. 12. Sieve Analysis
  13. 13. Sieve Designation - Large Sieves larger than the #4 sieve are designated by the size of the openings in the sieve
  14. 14. Review Activity 2 <ul><li>Commonly used larger size sieves </li></ul><ul><ul><li>3 inch </li></ul></ul><ul><ul><li>2 inch </li></ul></ul><ul><ul><li>1-1/2 inch </li></ul></ul><ul><ul><li>1 inch </li></ul></ul><ul><ul><li>3/4 inch </li></ul></ul><ul><ul><li>1/2 inch </li></ul></ul><ul><ul><li>3/8 inch </li></ul></ul>
  15. 15. Sieve Designation - Smaller 10 openings per inch # 10 sieve Smaller sieves are numbered according to the number of openings per inch 1-inch
  16. 16. Review Activity 3 <ul><li>Commonly used smaller size sieves </li></ul><ul><ul><li># 4 </li></ul></ul><ul><ul><li># 10 </li></ul></ul><ul><ul><li># 20 </li></ul></ul><ul><ul><li># 40 </li></ul></ul><ul><ul><li># 60 </li></ul></ul><ul><ul><li># 140 </li></ul></ul><ul><ul><li># 200 </li></ul></ul>
  17. 17. Activity 4, 5 & 7 (skip 6) <ul><li>Class Exercise - Convert weights retained to percent retained </li></ul><ul><li>Convert percent retained to percent finer </li></ul><ul><li>Plot Data on Form </li></ul>
  18. 18. Grain-size Distribution % Finer Grain Size, millimeters (log 10 ) Sieve Designation # 20 81
  19. 19. Particle Size Definition <ul><li>System based only on particles smaller than 3-inches </li></ul><ul><li>Cobbles are 3”to 12” </li></ul><ul><li>Boulders are > 12” </li></ul>
  20. 20. Gravel / Sand / Fines <ul><li>Gravels are between # 4 sieve and 3” </li></ul><ul><li>Sands are between # 200 sieve and # 4 sieve </li></ul><ul><li>Fines are smaller than # 200 sieve </li></ul>
  21. 21. Parameters Used in Classification System <ul><li>Particle Size </li></ul><ul><li>Water Holding and Plasticity </li></ul><ul><li>Organic Content </li></ul>
  22. 22. Tests to Define Boundaries <ul><li>Water Content - Definition </li></ul><ul><ul><li>Ratio of the weight of water in a sample to the weight of the dry soil </li></ul></ul><ul><ul><li>Expressed as a percentage </li></ul></ul><ul><ul><li>Values greater than 100 % possible </li></ul></ul>
  23. 23. Activity 8 Water Content
  24. 24. Water Holding and Plasticity <ul><li>Consistency States of Finer Particles </li></ul><ul><ul><li>Liquid </li></ul></ul><ul><ul><li>Plastic </li></ul></ul><ul><ul><li>Semi-solid </li></ul></ul><ul><ul><li>solid </li></ul></ul>Increasing Water Contents
  25. 25. Activity 9 Consistency States
  26. 26. Tests to Define Boundaries <ul><li>Tests are only performed on the fraction of a sample that is finer than the # 40 sieve. </li></ul>
  27. 27. Liquid Limit Definition <ul><li>The water content at which a soil changes from a plastic consistency to a liquid consistency </li></ul><ul><li>Defined by Laboratory Test concept developed by Atterberg in 1911. </li></ul>
  28. 28. Liquid Limit Definition <ul><li>The water content at which a groove cut in a soil paste will close upon 25 repeated drops of a brass cup with a rubber base </li></ul>
  29. 29. LL Test Procedure <ul><li>Prepare paste of soil finer than # 40 sieve </li></ul><ul><li>Place Soil in Cup </li></ul>
  30. 30. LL Test Procedure <ul><li>Cut groove in soil paste with standard grooving tool </li></ul>
  31. 31. LL Test Procedure <ul><li>Rotate cam and count number of blows of cup required to close groove by 1/2” </li></ul>
  32. 32. LL Test Procedure <ul><li>Perform on 3 to 4 specimens that bracket 25 blows to close groove </li></ul><ul><li>Obtain water content for each test </li></ul><ul><li>Plot water content versus number of blows on semi-log paper </li></ul>
  33. 33. LL Test Results Log N water content, % LL= w% Interpolate LL water content at 25 blows 25
  34. 34. Activity 10 Liquid Limit Problem
  35. 35. LL Values < 16 % not realistic 16 Liquid Limit, % PI, %
  36. 36. LL Values > 50 - HIGH Liquid Limit, % PI, % 50 H
  37. 37. LL Values < 50 - LOW Liquid Limit, % PI, % 50 L
  38. 38. Plastic Limit Definition <ul><li>The water content at which a soil changes from a plastic consistency to a semi-solid consistency </li></ul><ul><li>Defined by Laboratory Test concept developed by Atterberg in 1911. </li></ul>
  39. 39. Plastic Limit Definition - Activity 11 <ul><li>The water content at which a 1/8”thread of soil can be rolled out but it begins to crack and cannot then be re-rolled </li></ul>
  40. 40. Plastic Limit w% procedure <ul><li>Using paste from LL test, begin drying </li></ul><ul><li>May add dry soil or spread on plate and air-dry </li></ul><ul><li>Occasionally evaluate 1/8” thread </li></ul>
  41. 41. Plastic Limit w% procedure <ul><li>When point is reached where thread is cracking and cannot be re-rolled to 1/8” diameter, collect at least 6 grams and measure water content. Defined plastic limit </li></ul>
  42. 42. Definition of Plasticity Index <ul><li>Plasticity Index is the numerical difference between the Liquid Limit w% and the Plastic Limit w% </li></ul>w% LL PL PI = LL - PL
  43. 43. Definition of Plasticity Index <ul><li>It represents the range in water contents over which a soil behaves in a plastic manner </li></ul>w% LL PL PI = LL - PL liquid semi-solid plastic (remoldable)
  44. 44. Definition of Nonplastic <ul><li>If the soil has a PI of zero, or either of the Atterberg tests cannot be performed, the soil is said to be non-plastic </li></ul>
  45. 45. Complete Activity 11
  46. 46. Complete Activity 13 Comprehensive Review Terms and Definitions
  47. 47. Definition of Plasticity “ A- Line” Plastic soils plot above the A-Line on a Chart Plastic Soils
  48. 48. Definition of Plasticity “ A- Line” Non-plastic or slightly plastic soils plot below the A-Line on a Chart Nonplastic Soils
  49. 49. U-Line Significance “ U- Line” Correct tests never plot above U-line and LL values are never < 16 Unrealistic 16
  50. 50. Plasticity Chart
  51. 51. Example Plot of LL, PI Plastic or Not ??
  52. 52. Parameters Used in Classification System <ul><li>Particle Size </li></ul><ul><li>Water Holding and Plasticity </li></ul><ul><li>Organic Content </li></ul>
  53. 53. Criterion for Organic Designation <ul><li>A liquid limit test is performed on: </li></ul><ul><ul><li>One sample that is only air-dried </li></ul></ul><ul><ul><li>On another that is oven-dried prior to testing </li></ul></ul><ul><ul><li>The liquid limit values are compared by computing the ratio of the 2 values </li></ul></ul>
  54. 54. Organic Definition <ul><li>If the ratio of the oven-dried soil’s LL to the air-dry soil’s LL values is < 0.75, the soil is organic by definition. </li></ul><ul><li>If the air-dry LL is 50 or more, it is a HIGH liquid limit </li></ul><ul><li>If the air-dry LL is less than 50, the soil has a LOW LL value </li></ul>
  55. 55. Additional Evaluations of Organic Soils <ul><li>Ignition test. ASTM D2974 </li></ul><ul><li>Soil sample heated in muffle furnace set at either 440  or 750  Centigrade and weight loss measured. </li></ul><ul><li>Peat Classification D4427 </li></ul>