CBR Test

The CBR (California Bearing Ratio) test is used to evaluate the relative strength and bearing capacity of a soil by measuring its resistance to penetration under controlled loading condition and comparing it in terms of ratio with the penetration resistance offered by standard crushed stone material. The penetration loading is provided in terms of standard penetration value (usually 2.5 mm or 5 mm). The test material used for this test is a soil sample passing through 19 mm sieve and can be both disturbed or undisturbed.

CBR test is carried out mainly for soaked and unsoaked soil sample. For soaked sample, the soil sample is saturated prior testing. The main purpose of soaking is to assess the strength and bearing capacity of soil under loading at its saturated condition. Hence, this test is useful for evaluating the soil’s behavior in areas with high groundwater levels. Soaked sample CBR test is carried out to draft information for designing foundations, pavements etc.
Whereas for unsoaked sample, the soil sample is tested in its moisture condition and hence, the soil properties are assessed for loading condition in its natural or relatively dry state.