Soils may be stratified by the deposition of different materials in layers which possess different permeability characteristics. In such stratified soils engineers desire to have the average permeability either "in the horizontal or vertical directions. The average. permeability can be computed if the permeabilities of each layer are determined in the laboratory. The procedure is as follows:
kI , k2, ••• , kn = hydraulic conductivities of individual strata of soil either in the vertical or horizontal direction.