The three primary mechanisms of soil compaction, as identified by Lars Forssblad (1981), are static pressure, impact force, and vibration. Different compaction equipment utilizes one or a combination of these actions to achieve soil densification.
Vibratory tampers, for instance, primarily rely on impact force to compact soil. The repeated impacts break down soil aggregates and rearrange particles into a denser configuration. On the other hand, vibratory rollers employ a combination of static pressure and vibration to achieve compaction. The static pressure exerted by the roller’s weight enhances the effectiveness of the vibrations, leading to improved soil density.
The choice of compaction method depends on the type of soil being compacted. For sandy soils, vibration alone is often sufficient for achieving desired levels of compaction. The vibratory action disrupts the frictional forces between sand particles, allowing them to rearrange into a denser state.
However, for cohesive soils like clays, the combination of vibration and static pressure is necessary. Cohesive soils exhibit strong interparticle bonds, which require the shearing action of static pressure to break them down and facilitate compaction. The vibratory action then helps to rearrange the loosened particles into a denser structure.
In essence, understanding the different mechanisms of compaction and their applicability to various soil types is crucial for selecting the appropriate equipment and techniques to achieve optimal results. By tailoring the compaction method to the specific soil characteristics, engineers can ensure efficient and effective soil densification, leading to improved foundation performance and overall project success.