What is CBR method?

The California Bearing Ratio (CBR) is a measure of the strength of the subgrade of a road or other paved area, and of the materials used in its construction. The ratio is measured using a standardized penetration test first developed by the California Division of Highways for highway engineering.

What is design CBR?

Flexible pavement design by CBR method is used to determine the total thickness of pavement. Generally there are two methods to design the pavement from CBR (California bearing ratio) value.

What is CBR formula?

C.B.R. = (PT/PS) X 100 4. The C.B.R. values are usually calculated for penetration of 2.5 mm and 5 mm. Generally the C.B.R. value at 2.5 mm will be greater than at 5 mm and in such a case/the former shall be taken as C.B.R. for design purpose.

What are the applications of CBR test in flexible pavement design?

The california bearing ratio test is penetration test meant for the evaluation of subgrade strength of roads and pavements. The results obtained by these tests are used with the empirical curves to determine the thickness of pavement and its component layers.

What are the different methods of preparation of CBR test specimens in the laboratory?

Preparation of remoulded samples for the CBR test can be made in several ways. However, commonly used methods are described here: (1) Static compression (2) Dynamic compaction by (a) using 2.5 or 4.5 kg rammer and (b) using vibrating hammer.

How many types of methods are there to design a flexible pavement?

three types
Explanation: There are three types of methods to design a flexible pavement they are empirical, semi empirical and theoretical method.

How do you use CBR?

The CBR test is performed by measuring the pressure required to penetrate a soil sample with a plunger of standard area. The measured pressure is then divided by the pressure required to achieve an equal penetration on a standard crushed rock material. The harder the surface, the higher the CBR value.

What is the CBR value?

CBR is the ratio expressed in percentage of force per unit area required to penetrate a soil mass with a standard circular plunger of 50 mm diameter at the rate of 1.25 mm/min to that required for corresponding penetration in a standard material. The ratio is usually determined for penetration of 2.5 and 5 mm .

What is the importance of CBR test?

The purpose of doing a CBR test is to find out the California Bearing Ratio (CBR) of a material which has to be used for the subgrade of flexible pavements. The actual quantity that concerns the strength of the subgrade material is Resilient Modulus though.

Why CBR test is performed?

The California Bearing Ratio or CBR test is performed in construction materials laboratories to evaluate the strength of soil subgrades and base course materials.