roller compactors.

1. CHAPTER- FIVE
ROLLERS
By: Debas D.
1
Ambo University
Department of Mechanical engineering

2. INTRODUCTION
 A roller is a compactor vehicle used to compact soil,
gravel, concrete, or asphalt in the construction work.
 compaction is the act of densifying the soil by
pressing soil particles together into close contact,
resulting in the expulsion of air and/or water from the
soil mass.
 The result of the compactive effort is to increase the
strength of an earth till or embankment.
 Compaction of the soil is obtained by various actions
and roller machines.
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3. INTRODUCTION
 Compaction of soil is attained by applying energy to
soil by one of the methods given below.
1. Static Weight
2. Impact
3. Vibration
4. Kneading action
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4. INTRODUCTION
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5. INTRODUCTION
Static Weight:
 Applied by smooth wheel rollers and pneumatic tyre
rollers.
 Compaction can not reach lower strata because of
internal friction of soil.
 So this compaction is especially good for granular soils
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6. INTRODUCTION
Impact Compaction:
 The equipment used for impact compaction are
tamping rollers and rammers.
 Impact reduces the internal friction of soil and
particles start moving towards voids easily.
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7. INTRODUCTION
Vibrating:
 Vibrating rollers and vibrating plates are used.
 In this system impact force penetrates down to
great depth.
 Vibration minimizes the internal friction of particles
and smaller particles move down to voids easily.
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8. INTRODUCTION
Kneading Action:
 In this system the compaction starts from a lower
level and comes upward.
 Kneading action is actually the application of shear
stress to soil.
 Sheep's foot roller (tamping rollers) and pneumatic
tire rollers are used.
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9. Types of rollers
There are different types of rollers:
1. Smooth wheeled roller
2. Pneumatic tyre roller
3. Sheep foot roller
4. Vibrating and tamping roller
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10. 1. Smooth wheeled roller
 Smooth wheeled rollers are of two types:
i. Static smooth wheeled roller
ii. Vibrating smooth wheeled roller
 The compacting efficiency depends on weight
,width and diameter of each roller.
 Suitable for wide range of soil preferably granular
soils such as sand, gravel, and crushed stones.
 It is also effective in smoothing surface of soils that
have been compacted by tamping rollers
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11. 1. Smooth wheeled roller
 The desirable speed and number of passes for
appropriate compaction of soil depends on the type
of soil and varies from location to location.
 In case of vibrating smooth wheeled rollers, the
drums are made to vibrate by employing rotating or
reciprocating mass.
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12. Figure: Smooth wheeled roller
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13. 2. Pneumatic tyre roller
 In this type number of pneumatic wheels are
mounted on two or more axels under a loading
platform ,pulled by tractor.
 In addition to the direct pressure due to rolling
there is also slight kneading action.
 They may also be small or large tired units. The
small tire units are usually have two tendon axle
with 4 to 9 tires on each axels.
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14. Pneumatic tyre roller
 Major advantages of Pneumatic tyre roller
are the ability to control the ground contact
pressure by:
a) Altering the weights of machines,
b) Increasing the number of wheels,
c) Increasing the tyre width
d) Changing the contact area of the tyre by
altering the contact pressure.
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15. Pneumatic tyre roller
Figure: Pneumatic tyre roller
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16. Pneumatic tyre roller
Tyre Overlap:
• There is some gap between the tyres provided in
front and rear tyres.This gap is filled with the
movement of tyre.
• To achieve uniform compaction effect and avoid
tyre marks, front and rear tyre are over lap.
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17. Pneumatic tyre roller
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18. 3.Sheep foot roller
This type of roller Contains a steel drum
including a number of projecting steel feet.
During rolling operation the soil under the
projecting feet get compacted and also
considerable kneading action to the soil.
When the drum rotates, the pads out of the soil
they kick to the material because of their shape.
They are suitable for compacting all fined
grained material but is generally not suitable for
use of cohesion less granular material.
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19. Figure:Sheep foot roller
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20. 4. Vibrating and tamping roller
Vibrating roller
 Vibratory compactor enhance the performance of
static weight machines by adding dynamic forces,
usually achieved by a rotating eccentrically
weighted shaft mounted inside the roller.
 Vibrations of vibrators arrange the particles by first
disturbing even the arranged ones.
 Vibrators are turned off during the reversed motion
of roller.
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21. Vibrating roller
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22. Vibrating roller
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23. Vibrating roller
 Very useful for granular materials.
 Combination of vibration and pressure is applied.
 Not good for cohesive soils.
They could be:
 Vibrating tamping rollers
 Vibrating steel-drum (smooth wheel) rollers
 Vibrating pneumatic rollers
 Vibrating plates or shoes (manually operated rammers)
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24. Main components of vibrating roller
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25. PRINCIPLE OF VIBRATORY ROLLERS
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The vibration is produced
by rotating the off-center
weights

26. Principle of vibratory compaction:
 Grains of soil are effected by periodically alternating
inertial forces.
 These forces make grain particles ‘floating’, so ordering is
progressed without friction.
 At vibratory compaction low amplitude high frequency
excitation is used for loose soil or for deep layers.
 High amplitude low frequency excitation is used for
cohesive soils in thin layers.
 Frequency of excitation should be close to characteristic
frequency of the soil
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27. VIBRATORY ROLLERS - AMPLITUDE
 It is the vertical displacement of the roller drum.
Amplitude of vibration is directly related to the
impact force.
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28. VIBRATORY ROLLERS - FREQUENCY
 The Frequency is Drum impacts per minute
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29. Effect of Characteristics of Vibratory Roller
• High amplitude and low frequency are used to
compact soft soils and to reach deeper zones while
low amplitude and high frequency are used for stiff
soils and shallow depth.
• Further High amplitude and low frequency setting
is used for compaction of a thick layer whereas low
amplitude and high frequency setting is used for
the compaction of thin layer.

30. • For example on a first pass the roller might use a high
amplitude and low frequency but at the fourth pass, it sets
itself with a low amplitude and high frequency.
• The effectiveness of compaction depends upon several
factors involving interaction between the equipment and the
soil being compacted. These factors include.
a) Operating Frequency :
 Frequency control the number of impacts per meter
between the drum and ground.
 Maximum compaction occurs when it vibrates near
resonant frequency.

31. Effect of Frequency
Fig . Effect of Frequency

32. b) Amplitude of vibration:
• It is the vertical displacement of the roller drum.
• Amplitude of vibration is directly linked to the impact force.
• Higher amplitude results in achieving higher thickness of
compacted material at minimum number of passes, thereby
improving productivity.
• Amplitude determines impact force
Fig. Effect of Amplitude

33. C) Speed of Travel :
• Slow speed results in closeness of impacts, whereas high speed results
in increase in the spacing of impacts.
• An even lower speed may be required for the initial passes.
Impact Spacing
Fig. Effect of Travel Speed

34. Ways of excitation:
 circular excitation: simple construction, single exciter unit eccentric should
always rotate in , eccentric should always rotate in direction of advancing
 directed excitation: double exciter unit, generates both compressing and
sharing forces in the soil simultaneously
 oscillation: the two exciter masses generate moment at the surface of the
drum creating compressing and sharing forces in the soil so , so grains are
ordered horizontally. Vertical force is provided by the weight of the drum
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35. 35

36. Tamping foot roller
 These rollers usually have steel padded wheels and
can be equipped with a small blade to help for
leveling the layer.
 As tamping rollers moves over the surface the feet
penetrate into the soil to mix and compact the soil
from bottom to top of the layer.
 Tamping foot roller is best dedicated to fine grained
soils.
Figure: Tamping foot roller
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37. Output of Compactors
 Compacted earthwork is measured in terms of
compacted volume in the fill.
 This can be found by multiplying the compacted
area by the thickness of the compacted layer.
 Usually the number of passes required to attain
necessary soil density is specified, and should be
considered while estimating production.
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38. Specification of rollers
 Caterpillar CS54B Smooth Drum Vibratory Soil Compactor
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39. Specification of rollers
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