1) Consider a soil sample that has three layers. The value of permeability of the second layer is twice that of the first layer & the value of permeability of the third layer is thrice that of the first layer. The depth of each layer is the same, i.e., 5m.
Find the average value of permeability parallel to the bedding plane?
- a) k
- b) 2k
- c) 3k
- d) 4k
Answer: b) 2k
Let 〖 K〗_1, 〖 K〗_2 & 〖 K〗_3 be the values of permeability of the three layers.
From the above numerical,
〖 K〗_1= k
〖 K〗_2 = 2k
〖 K〗_3 = 3k
〖 Z〗_1 = 〖 Z〗_2 = 〖 Z〗_3=5m
When the flow is parallel to the bedding plane, then the coefficient of permeability is,
K = ( 〖 K〗_1 Z_1+ K_2 Z_2+⋯+K_n Z_n)/Z
K = (5k+10k+15k)/15k
K = 2k
Hence the average value of permeability parallel to the bedding plane is twice the first layer’s permeability.