-
The soil profile below a lake with water level at elevation = 0 m and lake bottom at elevation = –10 m is shown in the figure, where k is the permeability coefficient. A piezometer (stand pipe) installed in the sand layer shows a reading of +10 m elevation. Assume that the piezometric head is uniform in the sand layer. The quantity of water (in m3/s) flowing into the lake from the sand layer through the silt layer per unit area of the lake bed is
-
- 1.5 × 10–6
- 2.0 × 10–6
- 1.0 × 10–6
- 0.5 × 10–6
Correct Option: C
By Darcy’s law
q = Ki A
We want q per unit area
| ∴ q = | K.i | A |
K = Co-efficient of permeability = 10–6 m/s
i = hydraulic gradient = L/h
L = Length of silt layer in direction of flow
L = 20 m. (from figure)
h = difference in water levels of the overhead and bottom of lake.
= 20 m. (from figure)
| ∴ q = K.i = K × | h |
| q = 10–6 × | 20 |
q = 1 × 10–6 m3 /sec
