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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

Compaction & Finishing

HMWK Ch 4 # 1,4,8

compaction
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
slide3
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
compactive forces
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
proctor tests
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
compaction specs
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
measuring field density
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
compaction equip
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
confined areas
Confined Areas
  • Small vibratory compactors and rollers
    • F 5-6 – 5-8
    • Especially important to get compaction next to walls and footings
selection of equip
Selection of Equip
  • T 5-2, F 5-10
compaction operations
Compaction operations
  • Variables:
    • Moisture content
    • Lift thickness
    • Number of passes
    • Ground contact pressure
    • Compactor weight
    • Compactor speed
    • F 5-11
slide12
Thin lifts (5 – 8 inches)
  • 12 “ with heavy pneumatic rollers but may need precompaction
  • Vibratory compactors
    • 8” for 1 ton
    • 48” for 15 ton
slide13
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
production
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
job management
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
ground modification
Ground Modification
  • Soil stabilization
    • T 5-4
    • Soil surcharging
    • Sand columns to drain soil
    • Wicks forced into soil
    • Electroosmosis – uses electricity
ground modification1
Ground Modification
  • Reinforcement
    • Confinement
    • Inclusions
    • Minipiles
    • Soil nailing
    • Stone columns
ground modification2
Ground Modification
  • Physiochemical
    • Adding
      • Granular materials
      • Portland cement
      • Lime
      • Asphalt
      • Slurry walls
grading
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
job management1
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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