Abstract: The pore pressure in Terzaghi's effective stress equation denotes the one caused by infiltration of water from the boundary of the soil mass or the one another induced by external load. In some cases it denotes the overall effects of these two types. The type of pore pressure, which the engineer chooses in the analysis, varies with the purpose of his analysis. The value of infiltration-induced pore pressure resolved upon the flow net is determined by the electric analog method, and that of external load-induced pore pressure is usually measured in triaxial tests as the initial value dissipating with time. The overall effects of the two types of pore pressure depend upon the type of pore pressure, order of their occurrence as well as the type of soils.