Contents

  • Cover
  • Introduction
  • Essentials
    • Identifying and managing risk
    • Starting the job – be prepared
    • The job is not finished until it is signed-off
  • Basics
    • Roading terms
    • Basics about soil
  • Good construction
    • A well-constructed road
    • A well-constructed landing
  • Earthworks
    • Clearing and stripping
    • Cut and sidecast construction
    • Cut and bench fill construction
    • Full bench construction with end-haul
    • Earthworks compaction
    • Forming the landing
    • Forming curves and in-bends
    • Stabilising cut/fill slopes
    • Fixing weak formation
    • Final grading before metalling
  • Water control
    • Water control overview
    • Water table drains
    • Water table drainage culverts
    • Berms and cut-outs
    • Flumes
    • Silt traps
    • Silt fences
  • Culvert waterway crossings
  • Temporary bridges
  • Metalling
  • Maintenance of roads
    • General maintenance
    • Maintenance of new roads
    • Maintenance of harvesting roads
    • Maintenance of low-use roads
  • Assisting loggers and harvesting rehab
    • Installing deadmen
    • Harvesting track rehab
    • Landing rehab
  • Want to learn more?
  • Glossary

NZ Forest Road Engineering Manual: Operators Guide

  1.  ›
  2. Earthworks ›
  3. Earthworks compaction
 

Earthworks compaction

Why compact?

  • Compaction strengthens the fill and the road. It reduces the risk of fill movement or settlement on steep or unstable slopes.
  • It reduces the amount of road metal needed as road subgrade is stronger.
  • It helps protect or “seal off” earthworks from water penetration.
  • It can reduce repair and maintenance costs.

Which compactor for the job?

  • Compactor selection depends on the material.
  • Sheep or wedge foot rollers are the most useful in formation construction.
  • Vibrating drum rollers (smooth) are useful for sealing aggregate.
  • Heavy compactors work better.
  • Loaded metal truck wheels compact.
  • The correct compactor – a vibrating sheepfoot – has been used.
  • Optimum moisture content ensured good compaction. This varies depending on the material.
  • It is compacted in layers. The layer thickness is right for the material – it should not be more than 300 mm.
  • The material is not over-compacted.
  • Wide tracked machines apply low ground pressure even though they are heavy.
  • Dozers (and excavators) are not compactors.
  • Track rolling only gives minor compaction, but it tightens the fill by breaking down larger material.
  • The metal is being compacted with the correct compactor – a vibrating steel drum.
  • The aggregate is compacted in layers less than 150 mm.
  • Excessive vibrating rolling has brought moisture to the surface and hasn’t improved the result.
  • Do not try to compact wet or very dry materials, as these may become liquid.
  • Correct the moisture content by blending in other material or using a water cart for dry material.
  • Penetrometers are useful for identifying subgrade weaknesses.
  • They are good for finding problem areas along roads and tracks before grading.
  • They also show that the subgrade has met compaction standards.
  • Lack of compaction led to this major road failure.
  • Water will enter the tension cracks and make the fill even less stable.
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