Enter the pressure applied to the soil and the resulting deflection to calculate the subgrade modulus. The subgrade modulus is a measure of the soil’s stiffness and is used in pavement and foundation design.
Subgrade Modulus Formula
The following formula is used to calculate the subgrade modulus:
K = P / δ
Variables:
- K is the subgrade modulus (pci)
- P is the pressure applied to the soil (psi)
- δ is the deflection of the soil (inches)
To calculate the subgrade modulus, divide the pressure applied to the soil by the deflection of the soil.
What is Subgrade Modulus?
Subgrade modulus, also known as the modulus of subgrade reaction, is a measure of how much pressure is required to cause a unit of deflection in the subgrade. It is a critical parameter in the design of pavements and foundations, as it reflects the support characteristics of the soil or subgrade material beneath the structure. A higher subgrade modulus indicates a stiffer soil that can support more load with less deflection.
How to Calculate Subgrade Modulus?
The following steps outline how to calculate the Subgrade Modulus.
- First, determine the pressure applied to the soil (P) in pounds per square inch (psi).
- Next, determine the deflection of the soil (δ) in inches.
- Use the formula from above = K = P / δ.
- Finally, calculate the Subgrade Modulus (K) in pounds per cubic inch (pci).
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem:
Use the following variables as an example problem to test your knowledge.
Pressure applied to the soil (P) = 150 psi
Deflection of the soil (δ) = 0.5 inches
