I. Basic Concepts

Amplitude: The maximum vertical vibration distance of the drum, which determines impact force and compaction depth.

Frequency: The number of vibrations per minute, which determines compaction efficiency and uniformity.

II. Influence of Amplitude on Compaction Effect

Larger amplitude

• Stronger impact force, greater compaction depth.

• Better for difficult materials such as coarse-grained soil, thick layers, subgrade, and cement-stabilized layers.

• May loosen material or cause over-compaction, leading to surface bulging, cracking, and shoving.

• Suitable for: subgrade, base course, thick layers, coarse-grained materials.

Smaller amplitude

• Low impact force, shallow compaction (only surface layer).

• Gentle on fine-grained soil, thin layers, and asphalt surfaces, less likely to damage the structure.

• Uniform compaction and smooth surface.

• Suitable for: asphalt surface, thin layers, fine-grained soil, repair works.

III. Influence of Frequency on Compaction Effect

Higher frequency

• More impacts per unit time, higher compaction efficiency.

• More sufficient particle movement, more uniform density.

• Allows higher rolling speed and faster construction.

• Suitable for: most subgrades, cement-stabilized layers, middle and lower asphalt layers.

Lower frequency

• Fewer impacts, lower compaction efficiency.

• Heavier impact, suitable for extra-thick layers, large stones, and extremely hard materials.

• High speed easily causes incomplete compaction or unevenness.

IV. Matching Principles of Amplitude and Frequency

• Thick layers, coarse materials, subgrade: large amplitude + medium–high frequency

• Thin layers, fine materials, asphalt surface: small amplitude + high frequency

• Deep first, shallow later; strong first, weak later:large amplitude for base course, small amplitude for surface course.

• Frequency must match speed:high speed → high frequency; low speed → lower frequency allowed.