CLASSIFICATION OF COMPACTION EQUIPMENT
Compaction equipment can be
classified into four machine types,
each producing a different type of
compactive force:
1. Static
2. Ramming
3. Vibration
4. Combination
Static, Ramming and Vibration
The differences between ramming and vibratory action are basically the height the
machine will jump (amplitude) and the number of blows in a given time period
(frequency).
Static. This term applies to machines that use only their weight on the material for
compaction. Static rollers will only compact thin layers of soil.
Ramming. Rammers or Jumping Jacks are generally distinguished by their low
frequency (800 blows per minute) and high stroke 1-1/2 to 3-1/2 in. (38 to 90 mm). The
stroke of a rammer is the maximum height the ramming shoe or plate reaches from
ground level while operating.
Rammers are usually hand-held upright machines, which use a spring mechanism. The
ramming action breaks down the soil and forces the air out by pushing the soil particles
closer together.
The depth of compaction material (or lift) is usually limited to 8 inches (200 mm) or less.
Vibration. Vibratory machines are distinguished by high frequency of blows per minute
(2,000 to 6,000) and lower amplitude.
Each rotation of an eccentric generates a stress wave, which travels into the ground.
The purpose of this vibration is to set the soil particles in motion. The soil is broken
down and the particles are rearranged. As these particles rearrange themselves, they
force out the air trapped between them and fill the voids.
Walk-behind Vibratory Plate and Roller Compactors are capable of lifts up to 20 in. (500
mm) deep.
Combination Static, Ramming and Vibration. A Boom Mounted Vibratory Compactor
produces a dynamic force into the ground with a series of high frequency rapid impacts.
These dynamic forces are influenced by four main parameters: linear load, frequency,
amplitude and centrifugal force.
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