👉What Is CBR

💫CBR (California Bearing Ratio) is a soil strength test used mainly in road and pavement engineering to evaluate how well the soil can support loads.

🏷What CBR Means

⏺CBR compares the bearing capacity of a soil to that of a standard crushed stone (which is taken as 100%).

🔰CBR tells us how strong the soil is for road construction.

⭐️Why CBR Is Important

⚡️CBR is used to:

⏺Design road pavement thickness
⏺Check suitability of subgrade soil
⏺Design highways, airfields, and flexible pavements
⏺Decide if soil needs stabilization or replacement

🔰How CBR Is Determined

⏺A plunger is pressed into the soil at a standard rate
⏺The resistance of soil is measured
⏺This resistance is compared with standard crushed stone

🎲Typical CBR Values (Approximate)

⏺Very weak soil (clay, silt): 1–3%
⏺Poor soil: 3–5%
⏺Medium soil: 5–10%
⏺Good subgrade: 10–20%
⏺Gravel / crushed stone: 30–80%+

❇️Where the Test Is Done

⏺Laboratory CBR test
⏺Field CBR test

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