👉CBR method for flexible pavement thickness:

📌CBR (California Bearing Ratio) measures subgrade soil strength.
📌 Used to design flexible pavement thickness.
📌Pavement layers: Asphalt, Base, Sub-base, Compacted Subgrade.

📌Typical layer thicknesses:

🔗Asphalt – 100 mm,
🔗Base – 150 mm,
🔗Sub-base – 200 mm.

📌Steps:
  1. Determine CBR of subgrade.
  2. Use design chart/formula.
  3. Consider traffic load and material properties.

📌Subgrade classification:
  🔗Poor: 2–4% CBR
  🔗Average: 4–7% CBR
  🔗Good: 7–10% CBR

🎲Example: For CBR = 5%, recommended total thickness = 550 mm.

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