Permeability of Stratified Deposits  Print this page 
When a soil deposit consists of a number of horizontal layers having different permeabilities, the average value of permeability can be obtained separately for both vertical flow and horizontal flow, as k_{V}and k_{H} respectively. Consider a stratified soil having horizontal layers of thickness H_{1}, H_{2}, H_{3}, etc. with coefficients of permeability k_{1}, k_{2}, k_{3}, etc.
Let i be the equivalent hydraulic gradient over the total thickness H and let the hydraulic gradients in the layers be i_{1}, i_{2}, i_{3}, etc. respectively. where k_{V} = Average vertical permeability
The total head drop h across the layers is
Horizontal flow

