NPK C2D - Compaction Methods and Equipment Selection; COMPACTOR MODEL SIZE Vs PERFORMANCE

NPK
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COMPACTION METHODS AND EQUIPMENT
SELECTION
In order to achieve the desired level of effective compaction in the selected material, the
contractor must select the machine that produces the proper compactive effort.
GRANULAR SOILS
Granular material is not cohesive and the particles require a shaking or vibratory action
to move them. Boom mounted compactors are ideal for this application.
CLAY SOILS
Clay is cohesive and the particles stick together, therefore a high impact or impulse
force is necessary to ram the soil and force out the air to rearrange the particles. For
this soil, a larger model boom mounted compactor works best.
MIXED SOILS
Since soils are usually found as mixtures of clay and granular, machine selection
becomes more difficult. Generally, select the machine for the toughest application (the
most cohesive soil condition).
COMPACTOR MODEL SIZE vs PERFORMANCE
Lift. The lift height, or the depth of the loose fill being compacted, is an important factor
and affects the compactor model selection in two ways:
1. Performance
2. Cost of compaction
With the properly selected compactor model, soil compacts from the bottom of the lift to
the surface. As the compactor imparts energy into the soil, the stress wave travels to
the hard surface at the bottom of the lift and returns upward. This action sets the
particles in motion and compaction takes place. As the soil becomes compacted, these
stress waves have a shorter distance to travel and more force returns to the machine,
increasing the vibration at the machine.
If the lift is too deep for the compactor model, a layer of uncompacted soil will be
left.
It might seem that the biggest, most powerful model with the greatest compaction effort
is the best choice. That’s not always the case. In some situations, if the lift is too
shallow, it is possible to have too much compaction effort. Unfortunately, there is no
formula for determining how much compactive effort is enough - or too much. Different
jobs, compactor models, and materials will give different results.