# Blog Archives

## Soil Mechanics – Effective and Total Stress

Effective Stress, \(\sigma ‘\) is in units of pressure (Pa, \(\frac{kg*m}{s^2}\), \(\frac{F}{A}\), etc) and is given by this equation:

$$ \sigma ‘ = \sigma – u$$

Total stress, \(\sigma\), is the total amount of stress due to the soil at the depth you are considering:

$$ \sigma = \rho_s g z $$

\(\rho_s\) is the soil density (e.g. 80 lb/ft^3).

\(g\) is the acceleration of gravity (e.g. 32.2 ft/s^2).

\(z\) is the distance of the surface, or beginning of the soil section, to the point you are considering(e.g. 10 ft).