Compaction Equipment
There are two ways to compact the soil or subgrade—static force or vibratory force. Static force is simply the weight of the machine. Vibratory force uses some sort of mechanism to vibrate the soil, which reduces the friction between the soil particles, allowing them to squeeze together more easily.

Static force is sometimes sufficient for compaction of granular soils. Minnesota DOT
The type of soil (or subgrade material) determines the type of equipment needed for compaction:
- Cohesive soils need to be sheared to get compaction, so you need a machine that has high impact force. A rammer is the best choice, or for bigger jobs, a pad-foot roller (similar to a sheepsfoot roller). Lifts for compaction of cohesive soils should be no thicker than 6 inches.
- Granular soils only need the particles to be vibrated to move them closer together. Vibrating plates or rollers are the best choice. Lifts for gravel can be as thick as 12 inches; 10 inches for sand.
For big jobs, such as highways or large slabs, big ride-on vibratory rollers, either with smooth rollers or sheepsfoot rollers, are used for compaction. Walk-behind rollers, either with padded rollers that knead the soil, or with smooth vibrating rollers, are good for medium-sized jobs. For smaller jobs, the two most common types of compaction equipment are vibratory plate compactors (either one-way or reversible) and rammers.

Sheepsfoot rollers are used to compact cohesive soils.
Here are some details on each of the types of equipment:
- Rammers, sometimes called jumping jacks, vary in weight from about 130 pounds to 185 pounds. These tools are great for compacting the soil in a footing trench or for cohesive clays in smaller areas since they deliver a high impact force (high amplitude, lower frequency). They are not good for compacting granular materials—such as base courses.
- Vibratory plates are ideal for compacting granular soils and subbases. Available in weights of 100 to 250 pounds with plate size of 1 to 1.5 feet by 2 feet. The vibration is at a lower amplitude but higher frequency than with a rammer and is balanced to cause the machine to move forward.
- Reversible vibratory plates work well on granular soils or on with granular-cohesive mixes. With two eccentric weights, the vibration can be reversed to move the machine forward or backward or to stop to compress a single soft spot. For the money, these are good machines due to their versatility.

Rammers are great for compacting cohesive soils and in confined areas.
Wacker Neuson
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Vibratory plate compacters work well for compacting granular soils.
Wacker Neuson
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An excellent resource on soil compaction basics and equipment is Multiquip's Soil Compaction Handbook.
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