The compaction effectiveness of vibratory rollers is primarily determined by vibration frequency (Hz/rpm) and amplitude (mm), which together influence material density, compaction depth, and construction efficiency. Here’s a detailed analysis:

I. Impact of Vibration Frequency

Vibration frequency refers to the number of vibrations per minute (units: Hz or rpm).

1. High Frequency (40-50 Hz / 2400-3000 rpm)

• Applicable Materials:
  Asphalt mixtures, thin-layer stabilized soil (<10 cm).

• Effects:
  Rapid particle rearrangement improves surface density and smoothness.
  Reduces cracking risk in asphalt layers (often paired with low amplitude).

• Limitations:
  Limited effectiveness for deep compaction (e.g., subgrades).

2. Low Frequency (25-35 Hz / 1500-2100 rpm)

• Applicable Materials:
  Thick soil layers, gravel bases (20-50 cm).

• Effects:
  Deeper vibration transmission, suitable for high-thickness fills.
  Ideal for subgrades, dams, and high-load-bearing scenarios.

• Limitations:
  Poorer surface density; requires supplemental static compaction.

II. Impact of Amplitude

Amplitude refers to the vertical displacement of the drum (units: mm), categorized as high or low.

1. High Amplitude (1.5-2.0 mm)

• Applicable Materials:
  Loose, coarse-grained materials (e.g., crushed stone, sandy soil).

• Effects:
  Strong impact force breaks particles and compacts deep layers (30 cm+).
  Enhances overall stability of earthwork subgrades.

• Limitations:
  May crush asphalt aggregates or cause over-compaction.

2. Low Amplitude (0.4-0.8 mm)

• Applicable Materials:
  Asphalt surfaces, fine cohesive soils.

• Effects:
  Minimizes surface damage, ensuring smoothness.
  Ideal for final compaction to eliminate micro-voids.

• Limitations:
  Weak deep-layer compaction.

III. Combined Applications of Frequency & Amplitude

IV. Practical Adjustment Guidelines

• Asphalt Pavements:

• Initial compaction: Low freq. + medium amp. (e.g., 30 Hz/1.0 mm) for deep stability.

• Intermediate/final compaction: High freq. + low amp. (e.g., 45 Hz/0.6 mm) for surface density.

• Earthwork Subgrades:

• Layer-by-layer (20-30 cm per layer) with low freq. + high amp. (25 Hz/1.8 mm).

• Sensitive Areas:

• Near structures: Switch to oscillation mode (horizontal vibration) to reduce resonance.

V. Common Questions

❓ Why is high amplitude unsuitable for asphalt?
→ Risks aggregate crushing and "over-compaction" cracks.

❓ How to determine optimal settings?
→ Test with a density gauge (e.g., nuclear gauge). Increase frequency if surface is loose; raise amplitude if deep layers fail standards.

❓ Settings for double-drum rollers?
→ Front drum: Low freq. (deep compaction); Rear drum: High freq. (surface smoothing), e.g., 28 Hz + 42 Hz.

VI. Summary

• Frequency governs compaction speed and surface quality.

• Amplitude dictates compaction depth.

• Optimal combinations depend on material type, layer thickness, and project requirements.

• Always validate settings with test sections to avoid under-compaction or material damage!