:Methods of field compaction

2.  The various method of field compaction
1. Rolling
2. Ramming
3. Vibrations

3.  Different types of rollers are used for compaction of soils.
 The compaction depends upon the following factors.
 Contact pressure
 Number of passes (normally 5 to 15)
 Layer of thickness (less than 15cm)
 Speed of roller
 Different types of rollers used are
i. Smooth wheel rollers
ii. Pneumatic tyred rollers
iii. sheep foot rollers
iv. Track laying vehicles

4. Smooth wheel rollers
 Types of smooth wheel rollers
1. Conventional three wheel type having weight 2 to 15 ton.
2. Tendem rollers weight having 1 to 14 ton.
3. Three axle tendem roller having 12 to 18 ton.
 These rollers are useful for compacting granular base courses of
highway and runways.
 These are not effective for compaction of deep layers of soils.

5. Sheep foot Roller
 The sheep foot roller consists of a hollow
drum with a large number of small
projection on its surface.
 These projections penetrate the soil layers
during the rolling operations and cause
compaction.
 The drum can be filled with water to
increase the mass.
 The sheep-foot rollers are ideally suited
for compaction of cohesive soils.

7. Pneumatic tyred Rollers
 Pneumatic tyred Rollers use compressed air to
develop the required inflation pressure.
 The roller generally consists of 9 to 11 wheels
fixed on two axles, with the pneumatic tyres so
spaced that a complete coverage is obtained with
each pass of the roller.
 These rollers are effective for compacting
cohesive as well as cohensionless soil.

10.  A hand operated rammer consists of a block of iron,
about 3 to 5 kg in mass attached to a wooden rod.
 The rammer is lifted for about 0.30m and dropped on
the soil to be compacted.
 Tampers are used to compact soils adjacent to
existing structures such as trenches, within plinth of
building etc.

13.  In vibratory compactors, vibrations are induced in the
soil during compaction. The compactors are available in
a variety of forms.
 When the vibrator is mounted on a drum, it is called a
vibratory roller.
 These rollers are available both as pneumatic type and
the smooth wheel type.
 Another form of vibratory compactor is a vibrating plate
compactor.
 Hand operated vibrating plates are also available.
 The effect of the vibrating plates is limited to small
depths