DYNAMIC
COMPACTION
Dynamic compaction is a method that is used
to augment the density of the soil when definite subsurface constraints make
other methods unsuitable. It is used to boost the density of soil deposits. The
process involves of dropping a heavy weight frequently on the ground at repeatedly
spaced intervals. The weight and the height decide the amount of compaction
that would take place. The weight that is used depends on the degree of
compaction desired and is between 8 tone to 36 tone.
The height varies from 1m to 30m.
The impact of the free fall creates stress
waves that assist in the densification of the soil. These stress waves can go
through up to 10m. In cohesionless soils, these waves generate liquefaction
that is followed by the compaction of the soil. In cohesive soils, they generate
an increased amount of pore water pressure that is followed by the compaction
of the soil. Pore water pressure is the pressure of water that is intent within
the particles of rocks and soils.
The amount of compaction
depends on the weight of the hammer, the height from which the hammer is
dropped, and the spacing of the locations at which the hammer is dropped. The
initial weight dropping has the majority impact, and penetrates up to a larger
depth. The following drops, if spaced closer to one another, dense the
shallower layers and the process is completed by compacting the soil at the
surface.
Most soil types can be enhanced
with dynamic compaction. Old fills and granular soils are most frequently
treated. The soils that are underneath the water table have to be treated cautiously
to allow emission of the excess pore water pressure that is formed when the
weight is dropped onto the surface.
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