Description

California Bearing Ratio (CBR) Test

 

General. The test is an empirical test which gives an indication of the shear strength of a soil.

 

CBR values may vary from less than 1% on soft clays to over 150% on dense crushed rock samples.

1. Static compression
2. Dynamic compaction by

•    using 2.5 or 4.5 kg rammer and
•    Using vibrating hammer.

 

Undisturbed sample.

Only the CBR molds as described in 5.1.2.4(b) are suitable for undisturbed sampling.

Apparatus

The following apparatus is variously required to carry out the 2.5 kg, 4.5 kg and Vibrating hammer methods in Figure

• Test sieves of aperture sizes 20 mm and 5 mm.
• A cylindrical, corrosion-resistant, metal mold, i.e. the CBR mold, having a nominal internal diameter of 152±0.5 mm. . The mold is shown in Figure 4.3.3. The internal faces shall be smooth, clean and dry before each use.

 

• A compression device (load press) for static compaction, (for 2.5 kg hammer)

 

• Metal plugs, 152±0.5 mm in diameter and 50±1.0 mm thick, for static compaction of a soil specimen (for 2.5 kg hammer).

 

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