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California Bearing Ratio (CBR)

The California Bearing Ratio (CBR) test evaluates the strength of subgrade soil and pavement materials for flexible pavement design. It involves measuring the load required for a cylindrical plunger to penetrate the material at specified depths, with results expressed as a percentage of standard load values. The CBR method has been standardized by the Bureau of Indian Standards (BIS) and correlates with pavement thickness requirements for highways and airfields.

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13 views1 page

California Bearing Ratio (CBR)

The California Bearing Ratio (CBR) test evaluates the strength of subgrade soil and pavement materials for flexible pavement design. It involves measuring the load required for a cylindrical plunger to penetrate the material at specified depths, with results expressed as a percentage of standard load values. The CBR method has been standardized by the Bureau of Indian Standards (BIS) and correlates with pavement thickness requirements for highways and airfields.

Uploaded by

dhimanbaruah0052
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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CALIFORNIA BEARING RATIO (CBR)

The CBR test was developed by the California State Highway Department as a method for
evaluating the strength of subgrade soil and other pavement materials for the design and
construction of flexible pavements. The CBR test results have been correlated with flexible
pavement thickness requirements for highways and air fields. The CBR method of test has also
been standardised by the Bureau of Indian Standards (BIS).

The basic principle in CBR test is by causing a cylindrical plunger of 50 mm diameter to penetrate
into the specimen of soil or pavement component material at a rate of 1.25 mm per minute. The
loads required for 2.5 mm and 5.0 mm penetration of the plunger into the soil/material tested are
recorded. The CBR value of the material tested is expressed as a percentage of standard load value
in a standard material. The standard load values have been established based on a large number of
tests on standard crushed stone aggregates at the respective penetration levels of 2.5 and 5.0 mm.
These standard load values given below may directly be used to compute the CBR value of the
test material.

Penetration, mm Standard Load, kg

2.5 1370

5.0 2055

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