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CBR test on soil is type of
bearing test
shear test
penetration test
none of these
penetration test
The California Bearing Ratio (CBR) test is a penetration test used to evaluate the subgrade strength of roads and pavements. It measures the force per unit area required to penetrate a soil mass with a standard circular plunger of 50 mm diameter at a specified rate.
The California Bearing Ratio (CBR) test is a penetration test used to evaluate the subgrade strength of roads and pavements. It measures the force per unit area required to penetrate a soil mass with a standard circular plunger of 50 mm diameter at a specified rate.
CBR=PsтАЛPtтАЛтАЛ├Ч100 тАФ where PtтАЛ is the test load and PsтАЛ is the standard load for the same penetration.
The CBR test involves applying a load to a cylindrical soil specimen using a plunger at a constant rate of 1.25 mm/min. The pressure required to achieve 2.5 mm and 5.0 mm penetration is measured and expressed as a percentage of the standard load required to achieve the same penetration in a standard crushed rock material. The final CBR value is typically the higher of the two values calculated at 2.5 mm and 5.0 mm penetrations.
Plunger diameter is 50 mm.
Standard rate of penetration is 1.25 mm/min.
Usually performed on remolded or undisturbed soil samples.
The test evaluates the subgrade soil's suitability for pavement design.
Simple and easy to perform in the laboratory.
Widely accepted empirical method for pavement design.
It is an empirical test and does not measure fundamental mechanical properties like elastic modulus.
High sensitivity to moisture content and density of the sample.
Designing thickness of flexible pavements.
Classification of subgrade soil quality for road construction.
The standard loads for crushed stone are 1370 kg for 2.5 mm and 2055 kg for 5.0 mm penetration.
Option B is incorrect because while shear strength is related to bearing capacity, the CBR test mechanism specifically relies on measuring penetration resistance.
C is correct тАФ The CBR test is fundamentally classified as a penetration test because it measures the force required to force a standard plunger into the soil.
Always remember that CBR values are highly dependent on the compaction state and saturation level of the sample; therefore, the test should always be conducted at the specific field density intended for construction.