2. DEFINITION OF COMPACTION
Compaction is the process by
which soil particles are packed
more closely together by dynamic
loading such as rolling, tamping or
vibration it is achieved through the
reduction of air voids with little or
no change in water content of soil.
3. OBJECTIVES FOR COMPACTION
Compaction improves the engineering properties like
shear strength, density, permeability etc. of the f
Increasing the bearing capacity of foundations;
Decreasing the undesirable settlement of structures;
Control undesirable volume changes;
Reduces the chances of slope stability problems like
landslides.
Reduces the amount of water that can be held in the
soil by decreasing the void ratio and thus helps in
maintaining the required strength.
4. PURPOSE OF COMPACTION TEST:
The purpose of a laboratory compaction test is to
establish a relationship between dry density and
moisture content for a soil under controlled
conditions. R.R. Proctor (1933) was the first to
develop a method of assessing compacted fill that
has since become a universal standard and the
test is known as standard proctor test.
proctor test is also known as light compaction test
as per BIS.
AASHO developed a modified test to give a higher
standard of compaction and is known as modified
proctor test. The same is also known as heavy
compaction test as per BIS.
5. Laboratory compaction test
Standard
proctor test
Modified proctor
test
As per BIS(buero of Indian
standards)
Light compaction
test
Heavy compaction test
Detailsoftheapparatus
Cylindrical model
Internal diameter 100 mm 100 mm
Height 127.3 mm 127.3 mm
Volume 1000 cc 1000 cc
Rammer
Mass 2.6 kg 4.89 kg
Drop 310 450
Force diameter 50 mm 50 mm
Comp-active effort 592 kJ/m3 2700 kJ/m3
No. of layers compacted 3 5
No. of blows 25 25
Height of free fall 31 cm 45 cm
6. LIGHT COMPACTION TEST
Apparatus:
- cylindrical metal
mould
- rammer
- The mould is fitted
with detachable
base plate and
collar.
7.
8. Procedure :-
• The empty mould is
attached to the base
plate and weighed.
• The collar is then
attached to the mould
at the top.
• The wet and matured
soil is placed in the
mould and compacted
by giving 25 blows of
rammer uniformly
distributed over the
surface.
• The soil is compacted
in three layers.
9. The volume of soil taken in each layer is such that
its compacted height is about one third of the total
height of the mould.
Before placing the second layer, the top of the first
compacted layer is scratched for proper bonding of
both the layers.
The second and
third layers are also
compacted by
giving 25 blows of
rammer.
The collar is then
removed and
excess soil is
trimmed to level
10. The mould along with the compacted soil is then
weighed to get the mass of the compacted soil.
A representative sample is taken from the centre
of compacted soil for moisture content test.
The soil is then removed from the mould and is
mixed with the original sample.
About 2% more water
is added in the sample
and the test is
repeated.
The procedure is
continued until the
mass of compacted
soil begins to
11. The bulk density and dry density for the test is
calculated from the known values of mass of
soil, volume of soil equal to volume of mould
and the moisture content of each test
Bulk density
g= Mass of soil / Volume of Soil
= M/1000 gm/c.c.
Dry density of soil,
Yd=g /1+m gm/c.c.
where M = Mass of soil in gm
m = water content or moisture content
Volume of soil = Volume of mould = 1000 c.c.
12. A graph is plotted between % water content and dry
density the curve obtained is called compaction curve
as shown in figure.
It is clear from the graph that dry density of soil goes
on increasing as the water content is increased, till
maximum density is reached.
The water content corresponding to the maximum dry
density is called optimum moisture content (OMC).
13. HEAVY COMPACTION TEST
Also known as modified compaction test.
The modified proctor test was developed and
standardized by AASHO to represent heavier
compaction required for heavier transports.
The calculation of dry density and maximum dry
density is similar to that of standard proctor test.
Figure shows modified proctor test curve.
14. In this test, the water
content dry density curve
lies above the standard
proctor test dry density
curve lies above the
standard proctor test curve
and has its peak relatively
placed towards the left.
Thus for a same soil, the effect of heavier
compaction is to increase the maximum dry density
and to decrease the optimum water content.
The comp-active transmitted by the modified.
AASHO test hammer is about 4.5 times the energy
transmitted by Proctor’s hammer.
