Assessing the Strength of Substrate Beneath Roads and Paving

The California Bearing Ratio (CBR) test is a commonly used method for road, runway, or car park pavement design to evaluate the strength of the sub-grade.

This test involves driving a cylindrical flat-faced plunger with a defined area into the soil at a uniform rate. It can be performed at the surface or slightly deeper, typically at a 0.5 or 1m depth, depending on the soil or placed material of interest.

The test is dependent on a reaction force, often provided by a four-wheel-drive vehicle or a mechanical excavator.

This process allows for the assessment of the sub-grade strength, which is vital for designing robust road, runway, or car park pavements.