As suggested by
Lars Forssblad (1981), the three main
actions of compaction are static
pressure, impact force and vibration.
Different compactors contain one or more
modes of these actions. For example, vibratory
tampers perform mainly by the
principle of impact while vibratory
rollers work with principle of static pressure and vibration.
For sandy
soils, vibration is
adequate for normal
compaction because
the
action of
vibration sets the soil particles in
motion and friction forces
between soil particles are virtually demolished. During this vibration
motion,
the soil particles rearrange themselves to develop a dense state.
For clayey
soils, it is necessary to combine the action of vibration together with
static
pressure to breakdown the cohesion
forces between soil particles in order to allow for better compaction.
The
static pressure of vibratory machines is adopted to exert a shearing
force to
eliminate the cohesion in clayey soils.
