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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.
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 typeSoil moisture content Compaction effort required
Sheep foot
Pad foot
Vibratory Roller
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.
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.
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.
At this point, few air pockets remain – compaction forces are carried by water in soil which is incompressible
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• 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.
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• 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.
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• 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.
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• 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.
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•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.
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•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
Contractors Depot48 Island Drive, Eastpoint, Florida, 32328
http://www.concrete-catalog.com/soil_compaction.html
New York State Department of TransportationStandard Specifications.
