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Compaction lecture notes for civil engineering
- 1. 1 Compaction N. Sivakugan Duration = 10 minutes
- 2. SIVA Copyright©2001 2 What is compaction? A simple ground improvement technique, where the soil is densified through external compactive effort. + water = Compactive effort
- 3. SIVA Copyright©2001 3 Compaction Curve Water content Dry density ( d ) optimum water content d, max Soil grains densely packed - good strength and stiffness - low permeability
- 4. SIVA Copyright©2001 4 Compaction Curve What happens to the relative quantities of the three phases with addition of water? Water content Dry density ( d ) soil water air difficult to expel all air lowest void ratio and highest dry density at optimum w
- 5. SIVA Copyright©2001 5 Zero Air Void Curve All compaction points should lie to the left of ZAV curve - corresponds to 100% saturation Water content Dry density ( d ) Zero air void curve (S=100%) s w s d wG G 1 : Eq S<100% S>100% (impossible)
- 6. SIVA Copyright©2001 6 Effect of Compactive Effort Increasing compactive effort results in: E1 E2 (>E1) Lower optimum water content Higher maximum dry density Water content Dry density ( d )
- 7. SIVA Copyright©2001 7 Compaction and Clay Fabric Higher water content or higher compactive effort gives more dispersed fabric. more dispersed fabric more dispersed fabric Water content Dry density ( d )
- 8. SIVA Copyright©2001 8 Line of Optimum Water content Dry density ( d ) Compaction curves for different efforts Line of optimum
- 9. SIVA Copyright©2001 Filed Compaction Pneumatic rubber tired roller Different types of rollers (clockwise from right): Vibratory roller Smooth-wheel roller Sheepsfoot roller
- 10. SIVA Copyright©2001 10 Field Compaction Compacts effectively only to 200-300 mm; therefore, place the soil in shallow layers (lifts) Smooth Wheeled Roller
- 11. SIVA Copyright©2001 11 Field Compaction for compacting very small areas Vibrating Plates effective for granular soils
- 12. SIVA Copyright©2001 12 Field Compaction Provides kneading action; “walks out” after compaction Sheepsfoot Roller Very effective on clays
- 13. SIVA Copyright©2001 13 Field Compaction Provides deeper (2-3m) compaction. e.g., air field Impact Roller
- 14. SIVA Copyright©2001 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. SIVA Copyright©2001 15 Laboratory Compaction Test - to obtain the compaction curve and define the optimum water content and maximum dry density for a specific compactive effort. hammer Standard Proctor: Modified Proctor: • 3 layers • 25 blows per layer • 5 layers • 25 blows per layer • 2.7 kg hammer • 300 mm drop • 4.9 kg hammer • 450 mm drop 1000 ml compaction mould
- 16. SIVA Copyright©2001 16 Compaction Control Test compacted ground d,field = ? wfield = ? Compaction specifications Compare! w d
- 17. SIVA Copyright©2001 Dynamic Compaction - pounding the ground by a heavy weight Suitable for granular soils, land fills and karst terrain with sink holes. Crater created by the impact Pounder (Tamper) solution cavities in limestone (to be backfilled)
- 18. SIVA Copyright©2001 Dynamic Compaction Pounder (Tamper) Mass = 5-30 tonne Drop = 10-30 m
- 20. SIVA Copyright©2001 Vibroflotation Vibroflot (vibrating unit) Length = 2 – 3 m Diameter = 0.3 – 0.5 m Mass = 2 tonnes Practiced in several forms: vibro–compaction stone columns vibro-replacement Suitable for granular soils (lowered into the ground and vibrated)
- 27. SIVA Copyright©2001 27 Stone Columns vibrator makes a hole in the weak ground hole backfilled ..and compacted Densely compacted stone column
- 28. SIVA Copyright©2001 28 Blasting Aftermath of blasting Fireworks? For densifying granular soils
- 29. SIVA Copyright©2001 29 Earthmoving Equipment Large Excavator (see minivan on left for scale) David and Goliath?
- 30. SIVA Copyright©2001 30 Earthmoving Equipment Grader for spreading soil
- 31. SIVA Copyright©2001 31 Earthmoving Equipment Bulldozer for spreading soil evenly
- 34. SIVA Copyright©2001 34 Earthmoving Equipment Crawler mounted Hydraulic Excavator