Compaction finishing
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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

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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


Compaction finishing

  • 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


Compaction finishing

  • Thin lifts (5 – 8 inches)

  • 12 “ with heavy pneumatic rollers but may need precompaction

  • Vibratory compactors

    • 8” for 1 ton

    • 48” for 15 ton


Compaction finishing

  • 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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