What does the effective stress principle highlight in soil behavior?

The effective stress principle highlights the influence of pore pressure as a critical factor in determining soil behavior. In geotechnical engineering, effective stress is defined as the stress carried by the soil skeleton, which is the total stress minus the pore water pressure. This principle asserts that it is the effective stress that governs the strength and stability of soil.

When pore pressures increase, such as during heavy rainfall or construction activities, the effective stress reduces, which can lead to the soil losing strength and potentially causing issues like liquefaction or settlement. Conversely, when pore pressures decrease, the effective stress increases, enhancing the soil's load-bearing capacity.

Recognizing the significance of pore pressure in the effective stress principle helps engineers assess soil stability and design foundations and earth structures with a greater understanding of the soil's behavior under varying moisture conditions.