What is Compaction?
Compaction
It is a mechanical
process by which air is expelled out from soil mass to reduce the void and
densify the soil. It is measured by proctor test.
Factor Affecting Compaction
1. Water
content
2. Amount
of compaction
3. Type
of compaction
4. Types
of soil
5. Add
of admixture (CaSo4 is used to improve the density of soil)
Method of Compaction
a) Rolling : In
this method types of rollers are used. Some of them are described below :-
1. Smooth
wheel roller (Cohesion less soil)
2. Pneumatic
tyred roller (Cohesion less & Cohesive soil)
3. Sheep
foot roller (Cohesive soil)
b) Ramming :
This method is suitable for small area like trenches. Behind the bridge
abutment etc. it is suitable for both cohesive as well as cohesionless soil.
c)
Vibrating
1. Vibratory
roller – Cohesionless soil
2. Vibrating
plate compactor – Cohesionless soil- Monkey jumper
d) Vibrofloatation
: Cohesionless soil (Large thickness)
e) Falling method
: It is suitable for all types of soil in which a heavy weight (2 to 50t) is
fallen from a height (7 to 35m) depending upon the soil.
f)
Ponding
method
What is Consolidation?
Consolidation
It is a process,
which involves a gradual compression occurring simultaneously with a flow of
water out of soil mass and with a gradual transfer of applied pressure from the
pore water to mineral skeleton.
It may also be defined a process involving decrease in
the water content of a saturated soil without replacement of the water by air. It
is measured by oedometer or consoildometer.
Types of Consolidation
a)
Initial
Consolidation :
The
reduction in the volume of soil just after the application of the load is known
as initial consolidation. It is also known as immediate consolidation. For saturated
soil it occurs due to compression of solid particles.
b)
Primary
Consolidation :
The
reduction in the volume of soil after the completion of initial consolidation due
to expulsion of water for voids is known as primary consolidation.
c)
Secondary
Consolidation :
The
reduction on the volume of the soil at a very slow rate even after excess
hydrostatic pressure developed by the applied pressure in fully dissipated and
primary consolidation is complete. This additional reduction in volume is known
as secondary consolidation. The quantity of secondary consolidation is very
small
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Comparison Between Compaction and
Consolidation
Differences
Compaction
|
Consolidation
|
Rapid Process by mechanical means.
|
Gradual process under sustained
static loading.
|
Expulsion or air (Decrease
Volume)
|
Squeezing of water (Decrease
Volume)
|
Artificial process
|
Natural Process
|
It is almost instantaneous
|
It is time dependent.
|
Similarities
Compaction
|
Consolidation
|
Shear Strength increases
|
Shear Strength increases
|
Compressibility and permeability
decreases
|
Compressibility and permeability
decreases
|
Resulting in closer packing
|
Resulting in closer packing
|
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