Subgrade modulus is an important characteristic for determining the soil's supporting value.

• A. Not applicable
• B. True
• C. False
• D. Sometimes true

Answer: (B)

Subgrade modulus describes the soil’s stiffness under load, which directly controls how much support the soil can provide. It relates the pressure the soil surface can bear to how much the soil will deform or settle, so it’s a fundamental factor in predicting bearing capacity and settlement for any foundation resting on soil. A stiffer subgrade (higher modulus) resists deformation more, giving greater bearing support and less settlement, while a softer subgrade (lower modulus) yields more and can reduce the effective support the soil provides. Because the structure’s stability and performance—especially for tilt‑up panels sitting on grade—depend on how the soil reacts to loads, the subgrade modulus is a key parameter in determining the soil’s supporting value.