What does the California Bearing Ratio (CBR) test measure?

• A. Soil density
• B. Soil permeability
• C. Soil strength based on resistance to penetration
• D. Soil shear strength

Answer: (C)

The California Bearing Ratio (CBR) test measures soil strength based on its resistance to penetration. This test is critical in the field of civil engineering and transportation, particularly for evaluating subgrade soil strength in road construction. During the CBR test, a standard piston is driven into a soil sample at a controlled rate, and the pressure required to achieve a certain depth of penetration is measured.

The results are expressed as a ratio of the pressure required to penetrate the soil compared to the pressure required for the same penetration in a standard crushed rock material. CBR values help engineers determine the suitability of the subgrade for supporting pavement structures and are essential for designing roadways, highways, and other transportation facilities. A higher CBR value indicates a stronger, more stable soil that will effectively support loads without excessive deformation.

In summary, the CBR test is directly focused on assessing the strength of soil in terms of its load-bearing capacity, which is crucial for ensuring the longevity and durability of transportation infrastructures.