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Compaction

Compaction. N. Sivakugan. Duration = 10 minutes. What is compaction?. A simple ground improvement technique, where the soil is densified through external compactive effort. Compactive effort. + water =. Dry density (  d ).  d, max. optimum water content. Water content.

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Compaction

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  1. Compaction N. Sivakugan Duration = 10 minutes

  2. What is compaction? A simple ground improvement technique, where the soil is densified through external compactive effort. Compactive effort + water =

  3. Dry density (d) d, max optimum water content Water content Compaction Curve Soil grains densely packed - good strength and stiffness - low permeability

  4. air water soil Dry density (d) difficult to expel all air lowest void ratio and highest dry density at optimum w Water content Compaction Curve What happens to the relative quantities of the three phases with addition of water?

  5. Dry density (d) Zero air void curve (S=100%) Water content Zero Air Void Curve - corresponds to 100% saturation S<100% S>100% (impossible) All compaction points should lie to the left of ZAV curve

  6. Dry density (d) E2 (>E1) E1 Water content Effect of Compactive Effort Increasing compactive effort results in: • Lower optimum water content • Higher maximum dry density

  7. Dry density (d) more dispersed fabric more dispersed fabric Water content Compaction and Clay Fabric Higher water content or higher compactive effort gives more dispersed fabric.

  8. Dry density (d) Compaction curves for different efforts Line of optimum Water content Line of Optimum

  9. Filed Compaction Different types of rollers (clockwise from right): • Pneumatic rubber tired roller • Smooth-wheel roller • Vibratory roller • Sheepsfoot roller

  10. Field Compaction Smooth Wheeled Roller Compacts effectively only to 200-300 mm; therefore, place the soil in shallow layers (lifts)

  11. Field Compaction Vibrating Plates • for compacting very small areas • effective for granular soils

  12. Field Compaction Sheepsfoot Roller • Provides kneading action; “walks out” after compaction • Very effective on clays

  13. Field Compaction Impact Roller • Provides deeper (2-3m) compaction. e.g., air field

  14. Compaction Control • a systematic exercise where you check at regular intervals whether the compaction was done to specifications. e.g., 1 test per 1000 m3 of compacted soil • Minimum dry density • Range of water content • Field measurements (of d) obtained using • sand cone • nuclear density meter

  15. hammer 1000 ml compaction mould Laboratory Compaction Test • to obtain the compaction curve and define the optimum water content and maximum dry density for aspecific compactive effort. Modified Proctor: Standard Proctor: • 5 layers • 25 blows per layer • 3 layers • 25 blows per layer • 4.9 kg hammer • 450 mm drop • 2.7 kg hammer • 300 mm drop

  16. d d,field = ?wfield = ? w Compaction Control Test Compaction specifications Compare! compacted ground

  17. solution cavities in limestone Pounder (Tamper) Cratercreated by the impact Dynamic Compaction - pounding the ground by a heavy weight Suitable for granular soils, land fills and karst terrain with sink holes. (to be backfilled)

  18. Pounder (Tamper)Mass = 5-30 tonneDrop = 10-30 m Dynamic Compaction

  19. Dynamic Compaction

  20. Vibroflot (vibrating unit)Length = 2 – 3 mDiameter = 0.3 – 0.5 mMass = 2 tonnes Vibroflotation Suitable for granular soils • Practiced in several forms: • vibro–compaction • stone columns • vibro-replacement (lowered into the ground and vibrated)

  21. Vibroflotation

  22. Vibroflotation

  23. Vibroflotation

  24. Vibroflotation

  25. Vibroflotation

  26. Vibroflotation

  27. Stone Columns vibrator makes a hole in the weak ground ..and compacted Densely compacted stone column hole backfilled

  28. Blasting For densifying granular soils Aftermath of blasting Fireworks?

  29. Earthmoving Equipment David and Goliath? Large Excavator (see minivan on left for scale)

  30. Earthmoving Equipment Grader for spreading soil

  31. Earthmoving Equipment Bulldozer for spreading soil evenly

  32. Earthmoving Equipment Loader

  33. Earthmoving Equipment Backhoe

  34. Earthmoving Equipment Crawler mounted Hydraulic Excavator

  35. Earthmoving Equipment Rock Breaker

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