What LBR value is required for subgrade?

The LBR, or Lateral Bearing Ratio, is a crucial parameter used in the evaluation of subgrade materials in road construction and pavement design. An LBR value of 40 indicates a minimum acceptable strength for subgrade materials, ensuring adequate support for the pavement structure above.

When designing pavements, particularly for heavy traffic loads, it is essential to have a reliable subgrade that can adequately distribute stresses to prevent deformation and failure of the pavement layer. An LBR value of 40 demonstrates that the subgrade has the capability to support anticipated traffic loads, ensuring the durability and longevity of the pavement.

Values lower than 40 may not provide sufficient support, risking future settlement or cracking in the pavement. Higher LBR values may be required for specific applications or in areas with heavier loads, but for standard subgrade support, 40 is the standard threshold used in many guidelines, including by FDOT.