Soil compaction involves mechanically increasing the density of soil by reducing the amount of air in the soil. It is an important part of construction projects but must be done properly to avoid issues later. Key factors in soil compaction are the soil type, moisture content, and compaction effort required. Common compaction equipment includes sheep foot rollers, pad foot rollers, and vibratory rollers, which use static weight, kneading, and vibration to compact soils at varying depths. The amount of water in the soil also impacts compaction, as too little or too much water can reduce compaction effectiveness.

3.  Soil compaction is defined as the method of mechanically increasing the
density of soil by reducing volume of air.
 Method of mechanically increasing the density of soil.
 In construction, this is a significant part of the building process
 If performed improperly, settlement of the soil could occur and result in
unnecessary maintenance costs or structural failure.

4.  Soil is formed in place or deposited by various forces of nature - such as
glaciers, wind, lakes and rivers.
 Important elements in soil compaction:
Soil type
Soil moisture content
Compaction effort required

6.  Sheep foot
 Pad foot
 Vibratory Roller

7.  Static Force = deadweight of the machine, applying downward force
on the soil surface, compressing the soil particles.
 Static compaction is confined to upper soil layers and is limited to any
appreciable depth.
 Kneading is an example of static compaction.

9.  Vibratory force uses a mechanism, usually engine-driven, to create a
downward force in addition to the machine's static weight.
 The vibrating mechanism is usually a rotating eccentric weight or
piston/spring combination (in rammers).
 The compactors deliver a rapid sequence of blows (impacts) to the surface,
thereby affecting the top layers as well as deeper layers.
 Vibration moves through the material, setting particles in motion and
moving them closer together for the highest density possible.

16. Water lubricates the soil grains so that they slide more easily over each
other and can thus achieve a more densely packed arrangement.
A little bit of water facilitates compaction
too much water inhibits compaction.

17. At this point, few air
pockets remain –
compaction forces are
carried by water in soil
which is incompressible

19. 19

20. 20
• 100% coverage under the wheel
• Contact pressure up to 380 kPa
• Can be used on all soil types
except for rocky soils.
• Compactive effort: static weight
• The most common use of large
smooth wheel rollers is for proof-
rolling subgrades and compacting
asphalt pavement.

21. 21
• 80% coverage under the wheel
• Contact pressure up to 700 kPa
• Can be used for both granular and
fine-grained soils.
• Compactive effort: static weight
and kneading.
• Can be used for highway fills or
earth dam construction.

22. 22
• About 40% coverage
• Contact pressure is from 1400 to
8400 kPa
• It is best for compacting fine-
grained soils (silt and clay).
• Compactive effort: static weight
and kneading.

23. 23
• Has many round or rectangular
shaped protrusions or “feet”
attached to a steel drum
• 8% ~ 12 % coverage
• Contact pressure is from 1400 to
7000 kPa
• It is best suited for clayed soils.
• Compactive effort: static weight
and kneading.

24. 24
• 50% coverage
• Contact pressure is from 1400 to
6200 kPa
• It is ideally suited for compacting
rocky soils, gravels, and sands. With
high towing speed, the material is
vibrated, crushed, and impacted.
• Compactive effort: static weight and
vibration.

25. 25
• Vertical vibrator attached to smooth
wheel rollers.
• The best explanation of why roller
vibration causes densification of
granular soils is that particle
rearrangement occurs due to cyclic
deformation of the soil produced by
the oscillations of the roller.
• Compactive effort: static weight and
vibration.
• Suitable for granular soils

26. Contractors Depot48 Island Drive, Eastpoint,
Florida, 32328
http://www.concrete-catalog.com/soil_compaction.html
New York State Department of Transportation
Standard Specifications.