Objectives

1. Be able to use basic volume weight equations Understand principal of soil compaction. Explain how the compaction test is used in design and quality control Be able to perform basic compaction test(LAB EXERCISE) plot compaction data and evaluate for accuracy Understand procedure for Atterberg Limit Tests (LAB EXERCISE) Objectives

2. Review of Compaction Principles • Compaction Tests are not suitable for soils with more than 30 % by weight of the sample being larger than a ¾” sieve. • Compaction tests are not usually performed on soils with 12 % or fewer fines

3. Review of Compaction Principles • Relative Density testing is used for clean sands and gravels – covered later in class • Standard Procedures for testing are available for soils with some gravel (less than the maximum allowable content)

4. Principle of compaction • Theory developed by R.R. Proctor in 1930’s in California • Three Factors determine the density that results from soil compaction

5. Proctor Developed Principle • Three variables determine the density of a compacted soil • The energy used in compaction • The water content of the soil • The properties of the soil

6. State Diagram Dry Density, pcf 100 % saturation curve Water content, %

7. State Diagram Dry Density, pcf Water content, %

8. Energy Used in Compaction • Assume you have some clay soil that is at a water content of 16 percent. • Look at the effect different compaction energy has on the density of the soil. • Energy expressed as number of passes of a sheepsfoot roller on a lift of soil

9. 3 passes of equipment 4 passes of equipment 10 passes of equipment 2 passes of equipment 1 pass of equipment At this water content, energy has a large effect on compacted density Dry Density, pcf Water content, %

10. 10 passes of equipment At this point, the sample has had most of its air driven out by the compaction Dry Density, pcf 100 % saturation line Water content, %

11. 3 passes of equipment 4 passes of equipment 10 passes of equipment 2 passes of equipment 1 pass of equipment At a lower water content, energy has little effect on the compacted density of a clay soil Dry Density, pcf Water content, %

12. Compacting at low water contents • At low water contents, insufficient water is available to lubricate the particles and allow them to be rearranged into a dense structure. • The frictional resistance of dry particles is high

13. 3 passes of equipment 4 passes of equipment 10 passes of equipment 2 passes of equipment 1 pass of equipment At a very high water content, energy has little effect on the compacted density of a clay soil because the water is incompressible and takes the applied force without densifying the soil Dry Density, pcf This results in a term called pumping Water content, %

14. Compacting Very Wet Soil At this point, few air pockets remain – compaction forces are carried by water in soil which is incompressible

15. Water has Zero Shear Strength

16. Water has Zero Shear Strength

17. Effect of Water Content • Now examine the effect of just changing the water content on a clay soil, using the same energy each time the soil is compacted. • For example, assume soil is spread and compacted with 4 passes of a sheepsfoot roller each time. • Examine using State Diagram

18. Effect of Water Content Dry density, pcf 99.0 pcf Sample 1 compacted at 12 % water – Dry Density is 99.0 pcf 12 % Water content, %

19. Effect of Water Content Dry density, pcf Sample 2 compacted at 14 % water – Dry Density is 104.5 pcf 104.5pcf 14 % Water content, %

20. Effect of Water Content Dry density, pcf 105.5pcf Sample 3 compacted at 16 % water – Dry Density is 105.5 pcf 16 % Water content, %

21. Effect of Water Content Dry density, pcf Sample 4 compacted at 18 % water – Dry Density is 98.5 pcf 98.5 pcf Water content, % 18 %

22. Effect of Water Content @ constant energy Dry density, pcf Maximum dry density, pcf Optimum water content, % Water content, %

23. Now, perform the same test at a different (Higher energy) on the soil Dry density, pcf 10 passes of sheepsfoot roller 4 passes of sheepsfoot roller Water content, %

24. 80-95 pcf Effect of Soil Type on Curves Dry density, pcf Plastic Clay Soils have Low Values of Maximum Dry Density Water content, %

25. Plastic Clay Soils have high values for optimum water content (20-40 %) 20-40 % Effect of Soil Type on Curves Dry density, pcf Water content, %

26. Effect of Soil Type on Curves Dry density, pcf Plastic Clay Soils have a Flat Curve for Lower Energies Density Water content, %

27. Effect of Soil Type on Curves Dry density, pcf 115-135 pcf Sandy Soils with Lower PI’s have High Values of Maximum Dry Density Water content, %

28. Effect of Soil Type on Curves Dry density, pcf Sandy Soils with Lower PI’s have Low Values of Optimum Water Content 8-15 % Water content, %

29. Effect of Soil Type on Curves Dry density, pcf Sandy Soils have a Steep Curve – Short distance from plastic to liquid states of consistency Water content, %

30. Lower PI – Sandier Soils in this Region 110-135 Intermediate PI Soils in this Region 95-120 Higher PI – Clayey Soils in this Region 75-95 Summary Dry density, pcf Water content, %

31. Lower PI – Sandier Soils in this Region Higher PI – Clayey Soils in this Region 8-14 20-40 Summary Dry density, pcf Intermediate PI Soils in this Region 12-20 Water content, %

32. Family of Curves (Covered Later)

33. Family of Curves Zero air voids curve not parallel to line of optimums at upper end gd, dry density, pcf Line of Optimums water content, %

34. Proctor’s principle of compaction • Using a standard energy, if a series of specimens of a soil are compacted at increasing water contents, the resultant dry density of the specimens will vary. The density will increase to a peak value, then decrease.

35. Principle of Compaction • A plot of the dry density versus the water content from a compaction test will be parabolic in shape. • The peak of the curve is termed the maximum dry density, and the water content at which the peak occurs is the optimum water content.

36. Standard Proctor Energies • Several standard energies are used for laboratory compaction tests • Standard – 12,400 ft-lbs/ft3 • Modified – 56,000 ft-lbs/ft3 • California – 20,300 ft-lbs/ft3

37. Standard Proctor Compaction Test Summary 5.5 # hammer • Uses 5.5 pound hammer • dropped 12 inches • mold filled in 3 lifts • 25 blows of hammer per lift • Total energy is 12,400 ft-lbs/ft3 12”drop 3 lifts

38. Modified Proctor Compaction Test Summary 10 # hammer • Uses 10 pound hammer • dropped 12 inches • mold filled in 5 lifts • 25 blows of hammer per lift • Total energy is 12,400 ft-lbs/ft3 18”drop 5 lifts

39. Proctor Compaction Test Summary • Several Standard molds are used depending on maximum particle size in sample • 4”diameter mold (1/30 ft3) used for soils with low gravel contents • Method A for soils with < 20 % gravel • Method B for soils with > 20 % gravel and < 20 % larger than 3/8”

40. Proctor Compaction Test Summary • Several Standard molds are used depending on maximum particle size in sample • 6”diameter mold (1/13.33 ft3) used for soils with significant gravel contents • More than 20 % gravel larger than 3/8” • Must have less than 30 % larger than 3/4”

41. Proctor Compaction Test Summary • Standardized tests are not available for soils with more than 30 percent by weight of the total sample being larger than 3/4”in diameter gravels • ASTM Compaction Test Methods are • D698A D1557A • D698B D1557B • D698C D1557C

42. Proctor Compaction Test Summary • Prepare 4 to 5 specimens at increasing water contents about 2 % apart. Example - prepared samples at 14, 16, 18, and 20 percent. Use range of moistures based on feel and experience.

43. Proctor Compaction Test Summary Hammer • Then, compact each sample into a steel mold with standard procedures Cured soil Compaction mold

44. Proctor Compaction Test Summary • Then, strike off excess soil so the mold has a known volume of soil.

45. Proctor Compaction Test Summary • For each sample, measure the weight and the water content of the soil in the mold • The mold volume and weight are pre-measured. Don’t assume nominal volume of 1/30 ft3 or 1/13.33 ft3 • Calculate moist density • Calculate dry density • Plot dry density and water content for each point

46. Class Problem • Calculate Moist density, dry density

47. Class Problem Mold wt = 4.26 #, Mold Vol. = 0.03314 ft3

48. Class Problem • Calculate Moist density, dry density • Plot curve of dry density versus water content • Determine Maximum dry density and optimum water content

49. Set Up Plot – Form SCS-352 110 { 5 pounds 90

50. Set Up Plot – Form SCS-352 Make each vertical division equal to 1 percent water content