Soil compaction is one of the most critical components in the construction or roads, air-fields, embankments and foundations. The durability and stability of a structure are related to the achievement of proper soil compaction. Soil compaction is the process where by the practical of a soil are mechanically constrained to pack more closely Together or Soil compaction is the process of mechanical densifying a soil.

1. Principle and Equipment
of Soil Compaction
Submitted By: Shamsudin Masoud
Entry No:2017CET2531
Department of Civil Engineering
Indian Institute of Technology Delhi

2. Contents
• Introduction
• Factors influencing compaction of soil
• Effects of compaction on properties of soil
• Factor governing the suitability of equipment
• Types of Equipment
– Rammers
– Vibrating plate
– Vibro Tampers

3. Contents
• Types of Equipment
– Smooth wheeled Rollers
– Vibrating smooth wheeled rollers
– Sheepsfoot roller Roller
– Pneumatic Tyred Rollers
– Grid Rollers
– Pad Foot / Tamping Rollers
• References

4. Introduction
• Soil compaction is one of the most critical
components in the construction or roads, air-fields,
embankments and foundations.
• The durability and stability of a structure are related
to the achievement of proper soil compaction.
• Soil compaction is the process where by the
practical of a soil are mechanically constrained to
pack more closely Together or Soil compaction is
the process of mechanical densifying a soil.

5. Cont.…
• The process of compacting soil causes closer
packing of the soil particles, which in case of soft or
brittle particles may be assisted by the crushing of
the larger grains into smaller ones.
• This is achieved in general by the expulsion of air
form the soil and it results in a reduction in the
percentage of voids.
• In recent years great advances have been made in
knowledge of the principles involved and in the use
of heavy equipment for compacting soils in the field.

6. Factors influencing compaction of soil
• The effect of compaction upon the dry density of soil
mainly depends on the moisture-content of the soil
and on the amount of compaction applied and
mainly depend on the type of soil.
• With a soil of given moisture-content, increasing
amount of compaction result in closer packing of the
soil particles and in increased dry density, until the
volume of air remaining in the soil is so reduced that
further compaction produces no substantial change
in volume, the effect of the principal variables will be
considered in details.

7. Cont.…
• a) moisture content
– When the moisture content is low the soil is stiff
and difficult to compress, Thus low densities and
high air-content are obtained.
– As the moisture content increases the water acts
as a lubricant, causing the soil to soften and
become more workable, this results in higher
densities and lower air-content.
– Continue to increase with the moisture-content
and hence the dry density of the soil falls as
indicate in Fig.4

8. Cont.…
• a) moisture content

9. Cont.…
• b) Amount of compaction
– on all types of soil and with all methods of
compaction, increasing amount of compaction
result in an increase in the maximum density and
a decrease in the optimum moisture-content.
– Compering fig 5 curve, it will seen that above the
optimum moisture-content, when air voids are
large, the effect of increased compaction is
considerable,
– There is many experiment that we can measure
the effect of amount of compaction.

10. Cont.…
• b) Amount of compaction
– Fiq.5 shows the effects of increased amount

11. Cont.…
• b) Amount of compaction
– on all types of soil and with all methods of
compaction, increasing amount of compaction
result in an increase in the maximum density and
a decrease in the optimum moisture-content.
– Compering fig 5 curve, it will seen that above the
optimum moisture-content, when air voids are
large, the effect of increased compaction is
considerable,
– There is many experiment that we can measure
the effect of amount of compaction.

12. Cont.…
• C)Soil type
– The maximum density and the optimum moisture-
content both vary with the type of soil,
considering first cohesive soils, typical moisture/
density curves for a wide range of soils are
shown in fig.7.
– These curves were obtained by K.B.Woods by
classifying and averaging data on ohio soils.
– Curves of constant air voids for a particle density
of 2.70 have been superposed on woods curves.

13. Cont.…
• C)Soil type

14. Cont.…
• C)Soil type
– With increasing percentages of aggregate the
soils become sandy or gravelly and are termed
‘non-cohesive’ for these materials the sieve
analysis is the most important factor controlling
the density.
– Fig.8 also furnishes preliminary data for judging
the compaction properties of soils when only
limited test results are available .
– For example form a knowledge of the plastic limit,
a rough idea of the other soil constants can be
readily obtained.

15. Cont.…
• C)Soil type
– As indicated by the dotted lines, the range of experimental
points, however shows that such estimates should be
regarded as indications only.
– The effect of the presence of stones upon the compaction
of cohesive soil has recently been.
– With stone content exceeding 50 percent, contact between
made the material more difficult to compact and softening
of the soil mortar was found to assist compaction.
– The optimum moisture-content of the soil mortar was there
fore greater than when no stone was present.

16. Cont.…
• C)Soil type
– With increasing percentages of aggregate in the soil the
soil become sandy or gravelly and are termed “non-
cohesive” for these materials the sieve analysis is the most
important factor controlling the density.

17. Cont.…
• C)Soil type

18. Cont.…
• C)Admixture
– The effect of admixtures is chiefly of interest in stabilized
base construction.
– In general the admixture of electrolytes increases the
maximum density form 5 to 10 percent, and also
decreases the optimum moisture-content.
– Calcium chloride, which is used to improve gravel roads
has been found to increases the dry density of such
materials by as much as 11 percent.
– Sodium chloride increase the dry density up to 5 percent.
– Test made at the road research laboratory indicate that
effect of Portland cement in not very marked.

19. Cont.…
• C)Temperature
– Test by Hogentogler summarized in Table 3 indicate that
an increase in temperature increase the maximum density
and decreases the optimum moisture-content of soil,
although these effect are not very large, thery are
equivalent to the effects of several passes of the roller.

20. Effects of compaction on properties
of soil
• The object in compacting a soil is to improve its
properties .
– To increase its shear strength, the stability of a soil
depends upon its shear strength.
– Reduce its compressibility, the problem of settlements
under static and repeated loads is important, very little
work has been done.
– Decrease its water absorption, absorption of water by a
cohesive soil causes swelling and conversely, drying out
produces shrinkage
– Elasticity, the elastic properties of the soil depend upon its
state of compaction .

21. Effects of compaction on properties
of soil
• The object in compacting a soil is to improve its
properties .
– Permeability, although the state of compaction of a soil
affects the permeability, the effects are not very great.
– Weathering, in construction roads and runways on
compacted clay subgrades, its important to know the
extent to which the soil will retain its initial density.

22. Factor governing the suitability of equipment
– Selection of the most suitable compaction equipment.
– to meet specific conditions requires a knowledge of the
relative performance of the various types and also the
appropriate constructional techniques.
– In particular it is desirable to Know the various types of
Soil ,
• The effect of the amount of compaction upon the density obtainable.
• The most favorable moisture-content of the soil,
• The variation of density with depth
In this information cab be obtained only from field trials with
actual plant although certain conclusions follow form first
principles.

23. Types of Equipment
• There are different types of rollers and other soil
coaction equipment available
• The soil compaction equipment's can be divided in
to two groups.
– 1.Light soil compacting equipment's
• These equipment are used for soil compacting of small areas
only and where the compacting effort needed is less we will
explain the different type of these equipment in detail.
– 2.Heavy Soil compacting equipment's
• These compacting machines are used for large areas for use
on different types of soils, we will explain the different type of
these equipment in detail

24. Rammers
• Rammers are used for compacting small areas by
providing impact load to the soil.
• This equipment is light and can be hand or machine
operated .
Source of picture: https://theconstructor.org, Civil Engineering Home

25. Rammers
• The base size of rammer can be 15cmx15cm or
20cmx20cm or more.The usual weight varies
form 30kg to 10 tons.
• These hammers with 2 to 3 tons weights are
allowed to free fall from a height of 1m to 2m on
the soil for the compaction of rock fragments.
• Rammer are suitable for compacting
cohesive soil as well as other soil.

26. Vibrating plate
• Vibrating plate compactors are used for compaction
of Corse soils with 4 to 8% fines.
• These equipment are used for small areas.
• The usual weights of these machines vary form 100
kg to 2 tone with plate areas between 0.16 m2 and
1.6 m2.
Source of picture: https://theconstructor.org, Civil Engineering Home

27. Vibro Tampers
• Vibro tampers is used for compaction of small areas
in confined space.
• This machine is suitable for compaction of all types
of soil by vibrations set up in a base plate through a
spring activated by an engine driven reciprocating
mechanism.
• They are usually manually guided and weigh
between 50 and 100 kg (100 to 220 lbs).

28. Smooth wheeled Rollers
• The smooth wheeled rollers are of two types.
– Static smooth wheeled rollers
– Vibrating smooth wheeled rollers
• The most suitable soils for these roller type are well
graded sand, gravel, crushed rock, asphalt etc.
• These are used on soils which does not require
great pressure for compaction.
• These rollers are generally used for finishing the
upper surface of the soil,

29. Smooth wheeled Rollers
• These roller are not used for compaction of uniform
sands.
Source of picture: https://theconstructor.org, Civil Engineering Home

30. Smooth wheeled Rollers
• The performance of smooth wheeled rollers depend
on load per cm width it transfers to the soil and
diameter of the drum.
• The gross weight of these rollers is in the range of 8
to 10 tonnes(18000 to 22000 lbs).
• The other type of smooth wheel roller is called
tandem roller, which weighs between 6 to 8 tonne.
• The performance of these rollers can be increased
by increasing the increasing the weight of the drum
by ballasting the inside of drums with wet wand or
water.

31. Smooth wheeled Rollers
• Steel sections can also be used to increase the load
of the drum by mounting on the steel frame attached
with axle.
• The desirable speed and number of passes for
appropriate compaction of soil depends on the type
of soil and varies from location to location.
• About 8 passes are adequate for compacting 20 cm
layer.
• A speed of 3 to 6 kmph is considered appropriate for
smooth wheel rollers.

32. Vibrating smooth wheeled rollers
• In case of vibrating smooth wheeled rollers, the
drums are made to vibrate by employing rotating or
reciprocating mass.
• These rollers are helpful from several considerations
like:
– Higher compaction Level can be achieved with maximum
work.
– Compaction can be done up to greater depths
– Output is many times more than conventional rollers

33. Vibrating smooth wheeled rollers
Source of picture: https://theconstructor.org, Civil Engineering Home

34. Vibrating smooth wheeled rollers
• Although these rollers are expensive but in the long
term the cost becomes economical due to their
higher outputs and improved performance.
• The latest work specifications for excavation
recommends the use of vibratory rollers due to their
advantage over static smooth wheeled rollers.

35. Sheepsfoot roller Roller
• Sheepsfoot rollers are used for compacting fine
grained soil such as heavy clays and silty clays.
• Sheepsfoot rollers are used for compaction of soil in
dams, embankments, subgrade layers in pavements
and rail road construction projects.
• Sheepsfoot rollers are of static and vibratory types.
• Vibratory types rollers are used for compaction of all
fine grained soils and also soil with sand-gravel
mixes.
• Genrally this roller is used for compaction of
subgrade layers in road and rail projects.

36. Sheepsfoot roller Roller
Source of picture: https://theconstructor.org, Civil Engineering Home

37. Sheepsfoot roller Roller
• As seen in picture above, sheepsfoot rollers consist
of steel drums on which projecting lugs are fixed and
can apply a pressure up to 14kg/sqcm or more.
• Different types of lugs are namely spindle shaped
with widened base, prismatic and clubfoot type.
• The weight of drums can be increased as in the
case of smooth wheeled rollers by ballasting with
water, wet sand or by mounting steel sections.
• The compaction of soil is mainly due to foots
penetrating and exerting pressure on the soil .
• The pressure is maximum when a foot is vertical.

38. Pneumatic Tyred Rollers
• Pneumatic tyred rollers are also called as rubber
tyred rollers.
• These rollers are used for compaction of coarse
grained soils with some fines.
• These rollers are least suitable for uniform coarse
soil and rocks.
• Generally pneumatic tyred rollers are used in
pavement subgrade works both earth work and
bituminous works.

39. Pneumatic Tyred Rollers
Source of picture: https://theconstructor.org, Civil Engineering Home

40. Pneumatic Tyred Rollers
• Peneumatic rollers have wheels on both axles.
• These wheels are staggered for compaction of soil
layers with uniform pressure throughout the width of
the roller.
• The factors which affects the degree of compaction
are tyre inflation pressure and the area of the
contact.
• The latest rollers have an arrangement to inflate the
tyre to the desired pressure automatically.
• The total weight of the roller can be increased from
11 tone to 25 tone or more by ballasting with steel
sections or other means.

41. Grid Rollers
• Gird rollers are used for compaction of weathered
rocks, well graded coarse soil.
• These rollers are not suitable for clayey soils, silty
clays and uniform soils.
• The main use of these rollers are in subgrade and
sub-base in road constructions.
• These rollers have a cylindrical heavy steel surface
consisting of a network of steel bars forming a grid
with squire holes.
• Typical weights vary between 5.5 tone net 15 tone
ballasted .

42. Grid Rollers
Source of picture: https://theconstructor.org, Civil Engineering Home

43. Pad Foot / Tamping Rollers
• These rollers are similar to sheepsfoot rollers with
lugs of larger area than sheepsfoot rollers.
Source of picture: https://theconstructor.org, Civil Engineering Home

44. Pad Foot / Tamping Rollers
• The static pad foot rollers also called tamping rollers
have static weights in the range of 15 to 40 tone and
their static linear drum loads are between 30 to 80
kg/cm.
• These rollers are more preferable than sheeps foot
roller due to their high production capacity, and they
are replacing sheeps foot rollers.
• The density of soil achieved after compaction with
this roller is more uniform.
• These rollers also consists of leveling blades to
spread the material these are best suitable for
compacting cohesive soils.

45. References
• THE BASIC PRINCIPLES OF SOIL COMPACTION
AND THEIR APPLICATION, BY ALFRED HERBERT
DORENCOURT MARWICK,M.SC, M. INST. CE.
• https://theconstructor.org, The Contractor Civil
Engineering Home.