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CBR Test Calculation

The California Bearing Ratio (CBR) is calculated using the formula CBR (%) = (Test Load / Standard Load) × 100, with standard loads of 1370 kg for 2.5 mm penetration and 2055 kg for 5.0 mm penetration. Example calculations show a CBR of 40% at 2.5 mm with a test load of 548 kg and approximately 43.3% at 5.0 mm with a test load of 890 kg. The interpretation of results dictates which CBR value to use for design based on comparative results at the two penetration depths.

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649 views1 page

CBR Test Calculation

The California Bearing Ratio (CBR) is calculated using the formula CBR (%) = (Test Load / Standard Load) × 100, with standard loads of 1370 kg for 2.5 mm penetration and 2055 kg for 5.0 mm penetration. Example calculations show a CBR of 40% at 2.5 mm with a test load of 548 kg and approximately 43.3% at 5.0 mm with a test load of 890 kg. The interpretation of results dictates which CBR value to use for design based on comparative results at the two penetration depths.

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rahul020105
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California Bearing Ratio (CBR) Test

Calculation for California Bearing Ratio

The California Bearing Ratio (CBR) is calculated using the following formula:

CBR (%) = (Test Load / Standard Load) × 100

Where,
- Test Load = Load corresponding to a particular penetration value (e.g., 2.5 mm or 5.0 mm)
from proving ring
- Standard Load = Standard value of load for 100% CBR at that penetration

Standard Loads:
- For 2.5 mm penetration: 1370 kg
- For 5.0 mm penetration: 2055 kg

Example Calculation:
Suppose the load recorded at 2.5 mm penetration is 548 kg, then:

CBR = (548 / 1370) × 100 = 40%

Similarly, for 5.0 mm penetration with a load of 890 kg:

CBR = (890 / 2055) × 100 ≈ 43.3%

Interpretation:
- If CBR at 2.5 mm > CBR at 5.0 mm → Use CBR at 2.5 mm for design
- If CBR at 5.0 mm > CBR at 2.5 mm → Repeat the test to confirm. If results match, use CBR at
5.0 mm for design.

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