The primary effect of a piece of compaction equipment is usually to compress material under it by dead or static weight. There is also a kneading effect which is also desired.
A vibrating compactor shakes soil particles individually, causing a tendency to move into closer contact with each other. loose soil such as sand or clean gravel my be sufficiently compacted by vibration alone but usually it is desirable, and often essential to have weight on the vibrating surface.
many vibratory rollers are of an articulated construction, with engine and control section driving by means of a pair of large wheels which usually are rubber-tired.
vibrating rollers usually give best results when moving slowly. Vibration greatly increases roller effectiveness on loose, granular soils, but makes little difference on silt. The rule of thumb is “The larger the grain, the greater effect.