The Field CBR Test (California Bearing Ratio Test) is an in-situ test used to evaluate the strength of subgrade soil directly at the site. It measures the resistance of soil to penetration under controlled loading conditions and is widely used in road and pavement design. Basic Concept A standard plunger penetrates the soil Resistance offered by soil is measured Compared with standard crushed stone value Indicates load carrying capacity of subgrade Purpose of Field CBR Test For Soil: Determine subgrade strength Evaluate bearing capacity for pavements Study penetration resistance For Pavement Design: Design flexible pavements (bituminous roads) Decide thickness of pavement layers Assess compaction quality in field