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Compaction & Finishing

Compaction & Finishing. HMWK Ch 4 # 1,4,8. Compaction. Process of increasing density of soil by mechanically forcing soil particles closer together Not consolidation Used to improve soil

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Compaction & Finishing

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  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

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