Terzaghi's principle

Terzaghi's principle states that the effective stress in soil—which influences its strength and stability—is the total stress minus the pore water pressure. In simpler terms, when soil is loaded, part of that load is carried by water trapped between soil particles. The effective stress considers only the weight of the soil particles themselves, not the water pressure, which can weaken the soil's ability to hold together. This concept helps engineers analyze and predict soil behavior under different conditions, especially when designing foundations or assessing landslide risks.