Compaction Finishing

1. Compaction & Finishing HMWK Ch 4 # 1,4,8

2. Compaction Process of increasing density of soil by mechanically forcing soil particles closer together Not consolidation Used to improve soil Increased bearing strength, reduced compressibility, improved volume change characteristics, reduce permeability

3. Amount of compaction depends on Soil’s physical and chemical properties Moisture content Compaction method Amount of compactive effort Thickness of soil layer being compacted

4. Compactive Forces Static Weight – used by all Manipulation (kneading) – most effective in plastic soils Impact – low frequency blows (~10/sec) Vibration higher frequencies (<80 /sec) Impact and vibration good in plastic soils Vibration excellent in sands and gravels

5. Proctor Tests Standard and Modified Evaluates a soils moisture density relationship Do tests over a range of moisture contents to develop curve F 5-1 Moisture content at Maximum dry density => Optimum moisture content of soil F 5-2

6. Compaction Specs Ensure that the compacted material provides required engineering properties Use Proctor test to spec minimum density requirements Lack of uniformity may lead to differental settling

7. Measuring Field Density Liquid tests Measures volume of soil removed by measuring liquid required to fill hole Water is forced into a balloon to fill hole Sand test Fill hole and inverted cone over hole with sand Nuclear density sevice Measures reflected radioactivity to determine density

8. Compaction Equip Tamping foot rollers Grid or mesh rollers Vibratory compactors Steel wheel or smooth drum rollers Rubber tired rollers Segmented pad rollers Rammers and tampers – small impact compactors F 5-3

9. Confined Areas Small vibratory compactors and rollers F 5-6 – 5-8 Especially important to get compaction next to walls and footings

10. Selection of Equip T 5-2, F 5-10

11. Compaction operations Variables: Moisture content Lift thickness Number of passes Ground contact pressure Compactor weight Compactor speed F 5-11

12. Thin lifts (5 – 8 inches) 12 “ with heavy pneumatic rollers but may need precompaction Vibratory compactors 8” for 1 ton 48” for 15 ton

13. Repeated passes Usually 10 passes gets optimal density Ground contact pressure 30psi pneumatic roller 300 psi tamping foot roller Roller weight has bigger effect on density than contact pressure So more weight on same size pad = better compaction

14. Production Production (CCY/hr) = 16.3WSLE/P P = passes W = width compacted per pass S = compactor speed L = lift thickness E = job efficiency Rolling Resistance tamping foot rollers = 450 – 500 #/ton

15. Job Management Do test areas to get density right Hauling equipment gets right of way Would like to keep compacting and hauling in separate areas

16. Ground Modification Soil stabilization T 5-4 Soil surcharging Sand columns to drain soil Wicks forced into soil Electroosmosis – uses electricity

17. Ground Modification Reinforcement Confinement Inclusions Minipiles Soil nailing Stone columns

18. Ground Modification Physiochemical Adding Granular materials Portland cement Lime Asphalt Slurry walls

19. Grading Bringing earthwork to the desired shape and elevation Grader is standard tool F 5-13 F 5-15 Production Time = ((Sum of # of passes x Section length)/Average speed)x 1/efficiency

20. Job Management Use skilled operators Minimize turns For small projects back up do not turn around Grade side by side for large areas