In CBR test the value of CBR is calculated at

Explanation:

• The CBR test is a penetration test developed to evaluate the strength of subgrade soil, sub-base, and base course materials for roads and pavements.

• The CBR value is calculated by comparing the measured load on a soil sample to the standard load required to achieve the same penetration on a standard crushed stone material.

• Load values are recorded at various penetrations: 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 5.0 mm, 7.5 mm, 10.0 mm, and 12.5 mm.

• However, for determining the CBR value, the focus is primarily on: 2.5 mm, 5.0 mm penetration

Additional Information Standard Proctor Compaction Test

• Used to determine the optimum moisture content (OMC) and maximum dry density (MDD) of soil for compaction purposes.

• Involves compacting soil in a mould in three layers, each compacted with 25 blows of a 2.5 kg rammer falling from a height of 30 cm.

• Essential for earthwork design, embankment construction, and subgrade preparation.

Modified Proctor Compaction Test

• Similar to the standard test but uses higher compactive effort with a 4.9 kg rammer dropped from 45 cm.

• Provides higher MDD, suitable for heavy traffic pavements, airfields, or where high compaction is required.

• Helps in designing densely compacted layers with better strength and stability.