What is CBR California Bearing Ratio

The California Bearing Ratio (CBR) test is a straightforward robustness test that investigates the bearing limit of a material with that of a generally-reviewed pulverized stone (in this way, an amazing smashed stone material ought to have a CBR @ 100%). It is essential proposed for, but not restrained to, assessing the solidness of firm materials having most extreme molecule sizes less than 19 mm (0.75 in.) (AASHTO, 2000). It was improved by the California Division of Highways around 1930 and was therefore received by various states, areas, U.S. federal bureaus and globally. As an effect, most bureau and business geotechnical research facilities in the U.S. are provided to perform CBR tests.

The fundamental CBR test includes connecting stack to a minor entrance cylinder at a rate of 1.3 mm (0.05") for every moment and recording the sum stack at entrances going from 0.64 mm (0.025 in.) up to 7.62 mm (0.300 in.). Figure 1 is a sketch of a regular CBR specimen.

Equation

Values obtained are inserted into the following equation to obtain a CBR value:

Typical Values

General Soil Type	USC Soil Type	CBR Range
Coarse-grained soils	GW	40 - 80
	GP	30 - 60
	GM	20 - 60
	GC	20 - 40
	SW	20 - 40
	SP	10 - 40
	SM	10 - 40
	SC	5 - 20
Fine-grained soils	ML	15 or less
	CL LL < 50%	15 or less
	OL	5 or less
	MH	10 or less
	CH LL > 50%	15 or less
	OH	5 or less