To find Permeability in Stratified Soil deposits when direction of flow is parallel and perpendicular to strata.


To determine equivalent permeability in stratified soil deposits. 

(1)  When Direction of Flow is parallel (horizontal) to strata.

 


The Total discharge Q is the sum of discharge through individual layers (strata) hence Q=Q1+Q2+Q3.

Let Z1, Z2, Z3 within thickness of each layer where as K1,K2,K3 within coefficient of permeability for individual layers respectively as shown in figure.

The piezometric head for each layer remains constant i.e. h=h1=h2=h3
 Hence equivalent permeability in horizontal direction i.e. 'x' is
Kx or KH = K1Z1+K2Z2+K3Z3                     
                           ---------------------------------                           
                                 (Z1)(Z2)(Z3)



(2)  When Direction of Flow is perpendicular to strata



The Total discharge Q remains same through each layers (strata) hence Q=Q1=Q2=Q3.

Let Z1, Z2, Z3 within thickness of each layer where as K1,K2,K3 within coefficient of permeability for individual layers respectively as shown in figure.

The piezometric head for each layer remains constant i.e. h=h1+h2+h3
 Hence equivalent permeability in horizontal direction i.e. 'x' is
 Kx or KH =      Z1+Z2+Z3                     
                            ---------------------------------               
                    (Z1)/K1 + (Z2)/K2 + (Z3)/K3




Comment :- The Coefficient of permeability in horizontal direction is more as compare to that of vertical direction. KH > KV.



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