The compaction thickness of a roller is typically determined based on a comprehensive evaluation of soil type, material properties, roller model, and construction requirements. Below is a general reference range:

1. Standard Compaction Thickness

• Loose materials (e.g., sandy soil, gravel): Single-layer compaction thickness is usually 20–30 cm.

• Cohesive soil (e.g., clay, silt): Single-layer thickness is relatively thin, typically 15–25 cm, as clay requires higher compaction energy.

• Mixed fill materials: Approximately 20–40 cm, with specifics determined through test sections.

2. Influence of Roller Type

• Static rollers: Suitable for thin-layer compaction (15–25 cm), relying on self-weight for compaction.

• Vibratory rollers: Can handle thicker layers (25–50 cm), as vibration waves enhance deep-layer density.

• Impact rollers: Maximum thickness can reach 50–100 cm, ideal for large-scale fill projects.

3. Key Control Factors

• Material moisture content: Should be close to the optimal water content; otherwise, compaction effectiveness may be compromised.

• Number of passes: Typically 4–6 passes; excessive rolling may cause material breakdown.

• Layered construction: Each compacted layer must undergo density testing (e.g., ≥95% of standard compaction) before the next layer is laid.

4. Special Conditions

• Asphalt pavement: Paving thickness is usually 5–10 cm (hot-mix asphalt), with a post-compaction reduction of about 20%.

• High-fill subgrade: May involve layers exceeding 50 cm, requiring heavy-duty equipment.

5. Regulatory Standards

• Rock-fill subgrade: Each layer should not exceed 40 cm.

• Soil subgrade: Each layer should not exceed 30 cm.

• China’s Technical Specifications for Highway Subgrade Construction (JTG/T 3610-2019) recommends:

In practice, optimal parameters should be determined through test sections to ensure compaction density (e.g., ≥96% for expressway subgrades) and uniformity meet design requirements. Excessive thickness may result in loose lower layers, while insufficient thickness reduces efficiency.