Mechanical compaction, chemical compaction, Rollers, Compaction rate, formula, principle working of compactors.

1. CONSTRUCTION EQUIPMENT
(CM-104)
Chapter II – Compacting Equipment

2. SYLLABUS
 Soil Stabilization
 Soil Compaction
 Soil properties affecting Compaction
 Types Of Compacting Equipment
 Rollers
Sheep foot roller
Pneumatic roller
Vibrating roller
 Vibrating plates
 Vibrating Compaction

3. STABILIZATION
 Soil stabilization means the improvement of
the stability of the soil by Compaction or
Addition of suitable admixtures(stabilizers).
 It increases binding property between soil
particles.
 It improves a bearing capacity( power) of the
soil.

4. METHODS OF SOIL STABILIZATION
1.



2.

6. SOIL- BITUMEN STABILIZATION

7. COMPACTION
 Compaction is a densification of soil by mechanical
energy.
 It decreases volume of soil by expelling air from
partially saturated or dry soil.
 Rapid process
 Artificial process

8.  To increase the strength of soil
 To improve the stability of soil
 To reduce soil permeability
 To reduce erosion damage
 To reduce settlement of soil

9. EFFECT OF COMPACTION ON SOIL PROPERTIES
 Bearing capacity increase
 Void ratio decrease
 Permeability decreases
 Strength increases
 Settlement reduces

10. COMPACTION
Actions/Principals involved
 Impact
 Pressure
 Vibration
 Kneading

11. COMPACTION METHODS
Sr. No. Compactor Principal method
1 Sheep-foot rollers Pressure
2 Pneumatic rollers Pressure & Kneading
3 Vibrating rollers Impact & vibration
4 Tamping rollers Impact & pressure
5 Rammers Impact

12. ROLLERS
 Types:
 Cylindrical rollers
 Sheep-foot rollers
 Pneumatic rollers
 Smooth wheeled rollers
 Vibratory rollers
 Grid rollers

13. SHEEP-FOOT ROLLER
Suitability: All fine-grained soils

14. Schematic representative diagram
F :- Diameter of the wheel A :- length of roller
D :- Axle distance

15. SHEEP-FOOT ROLLER
Principal Pressure
Specialization Steel wheels with cylindrical feet ( area 30-80 sq.cm)
Ballast Water / dump sand
Speed 4 to 6 mph
No. of passes 6 to 10 passes for 8-in clay
Pressure Exerted Light – 4 to 7 Kg/cm2 Heavy – 25 to 70 Kg/cm2
• It also aerates soil while compacting, since can be used for soils having
moisture contents more than required.
• Does not compact top layers, therefore finishing should be done with
other type of rollers.

16. FACTORS GOVERNING THE COMPACTION
 Gross weight of the roller
 Area of each feet
 No. of feet
 Total no. of feet per drum
 Maximum pressure exerted on soil when foot is
vertical

17. ROLLER COMPACTION ESTIMATING
W : Compacted width per roller pass in feet
S : Average roller speed in mph
L : Compacted list thickness in inches
n : No. of roller passes required

18. PNEUMATIC ROLLERS
Suitability : Cold laid bituminous, closely graded, fine grained
Asphalt works, recycled pavements

19. Schematic representative diagram
A : Total length of equipment B : Axle distance

20. Principal Pressure & Kneading
Specialization Heavy wagon with several rows of closely spaced tyres
Ballast Steel sections
Speed 6 to 24 mph
No. of passes 8 passes for max density
Pressure Exerted 7 Kg/cm2
PNEUMATIC ROLLERS
• The flexible tyre surface permits efficiency over slightly irregular surfaces
which helps in maintaining uniform density & bearing capacity.
• They are efficient when used to finish off the embankment compacted by
sheep-foot roller.

21.  Tyre pressure
 Area of contact/tyre size
 Inflation pressure ( Pressure variance)
 Tyre ply
FACTORS GOVERNING THE COMPACTION

22. VIBRATING ROLLERS
Suitability : Sand, gravels, asphalt & granular surfaces

23. Schematic representative diagram

24. VIBRATING ROLLERS
Principal Impact & Vibration
Specialization Vibrating drum converts P.E. to K.E. to pack particles closely
Ballast Provision of eccentric shaft to produce required vibrations
Speed 2 to 4 mph
No. of passes Depends on the working speed
Pressure Exerted Weight of the equipment – 4 to 6 tonnes
• Vibrations normally vary from 1,000 to 5,000 rpm.
• It has two components :
Amplitude – measurement of movement
Frequency – measurement of vibrations per minute
• Amplitude controls the effective area/depth of compaction, while frequency
controls the vibration transmitted in a period of time.

25.  Frequency of the blows
 Time period
 No. of drums provided
 Vibratory rollers basically have two types of drums
 Single drum roller
 Two drum roller
FACTORS GOVERNING THE COMPACTION

26. SMOOTH WHEELED ROLLERS
Suitability : Gravel, sand, hard core, surface dressing

27. SCHEMATIC REPRESENTATIVE DIAGRAM

28. Principal Pressure
Specialization A large steel drum in front & one/two drums at rear
Ballast Water/wet sand
Speed 3 to 6 km/hr
No. of passes 8 passes for 20 cm layer
Pressure Exerted 10 to 17 Kg/cm2
SMOOTH WHEELED ROLLERS
•When the moisture content is slightly more optimum, it will compact
more easily.
•Steam roller can withstand high wear & tear & it is more easy to
operate but once it started it cannot be cut off for a small break.

29.  Load per cm width
 Diameter of the roll
FACTORS GOVERNING THE COMPACTION

30. VIBRATORY PLATES
Suitability : Granular soils, crushed aggregate & asphalt concrete

31. Principal Impact
Specialization A 4-stroke engine, diesel/gasoline operated
Speed 200 cm/s
Pressure exerted 10.5 KN
VIBRATORY PLATES
• These compactors gives efficiency where heavy & large compactors
cannot be operated or cannot be accessed.
• Remote controlled compactors can be operated from a certain distance to
protect worker from unfavorable conditions.

32.  Centrifugal force
 Exciter revolutions per minute
 Depth of vibration penetration
 Foot per minute travel
 Area of coverage per hour
FACTORS GOVERNING THE COMPACTION

33. DYNAMIC COMPACTION

34.  Heavy tamping, impact densification.
 Suitable on coarse grained soils
 Compaction depth : 35 ft
 Weight : 6-35 tons
 Drop heights : for cranes – 100 ft
DYNAMIC COMPACTION

35. QUESTIONS:
1) List types of Compactors and principal methods of
compaction. Also state suitability of each method with type of
soil. (Winter 2016)- 8 marks
2) What is meant by Soil stabilization ? Explain various soil
properties affecting the selection of compacting equipment.
(Winter 2015)- 6 marks
3) Explain with neat sketch working of Sheep-Footed roller.
Discuss the suitability of sheep footed roller as compacting
equipment. (Winter2015)- 6 marks
4) Explain Vibratory compactor. (Winter 2010)-
5) Discuss the salient features and suitability of
 Sheep footed roller
 Pneumatic roller (Winter 2010)