Compaction

Compaction tests typically enable the following criteria to be established: 

• The relationship between dry density and moisture content for a given degree of compactive effort.
• The moisture content for the most efficient compaction; that is, at which the maximum dry density is achieved under that compactive effort.
• The value of the maximum dry density achieved.

There are several different standard laboratory compaction tests, with the most appropriate in each case being based on the nature of the project, the type of soil and the availability of equipment on site.

Applications of Compaction

Soil used as fill:

• To refill an excavation or void
• To provide made-up ground to support a structure
• As a sub-base for a road, railway or airfield runway
• As a structure; e.g. an earth dam

Improvement by compaction

• Higher stability
• Higher CBR Value
• Lower compressibilty
• Lower permeability
• Lower frost susceptibility

Effect on mass of fill

• Greater stability
• Less settlement
• Less deformation
• Less water absorption
• Less risk of frost heave