Effective Stress Calculator - Calculator Academy

Choose effective stress, total normal stress, or pore water pressure, then enter the other two values in psi, kPa, or MPa.

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Effective Stress Formula

For saturated soil, the following relation calculates effective normal stress from total normal stress and gauge pore water pressure on a consistent pressure reference.

σ' = σ - u

Variables:

σ' is the effective stress
σ is the total stress
u is the pore water pressure

To calculate the effective stress, subtract the pore water pressure from the total stress.

What is Effective Stress?

Effective stress is a concept in soil mechanics that represents the stress carried by the soil skeleton. It is a crucial parameter in geotechnical engineering as it influences the strength and deformation behavior of soils. For saturated soil, effective normal stress is total normal stress minus pore water pressure. Compression is taken positive, and pore pressure is gauge pressure. Partially saturated soils require an appropriate extended model. This concept helps engineers understand how soils will behave under different loading conditions and is essential for designing stable foundations, retaining structures, and other geotechnical systems.

How to Calculate Effective Stress?

The following steps outline how to calculate the Effective Stress.

First, determine the total stress (σ) applied to the soil.
Next, determine the pore water pressure (u) within the soil.
Finally, calculate the effective stress using the formula σ' = σ - u.
After inserting the values 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.

Total Stress (σ) = 100 kPa

Pore Water Pressure (u) = 30 kPa