California Bearing ratio method

Basic principle: 

The basic principle of the CBR method of flexible pavement design is based on the concept that the total thickness of flexible pavement required mainly depends upon two factors.

i) CBR value of the soil subgrade over which pavement is to be laid.

(ii) the magnitude of the wheel load or intensity of traffic loads expected.

Advantages of CBR method: 

One of the main advantages is the simplicity of conducting the CBR test in the laboratory as well as the method of pavement design using simple design charts. The CBR method of flexible pavement design was being extensively used in different countries of the world for quite a long period of time.

Limitation of CBR method:

i) It is important to understand the limitations of the CBR test itself on subgrade soil which is an empirical penetration test for assessing the strength characteristics.

ii) The punching shear under the CBR test condition does not in any way represent the stress on the subgrade
through the flexible pavement layers due to traffic wheel loads.