Question

The spacing of tile drains to relieve water-logged land is directly proportional to the:-
1. depth of drain below the water level
2. coefficient of permeability of the soil to be drained
3. depth of drain below the ground surface
4. depth of impervious strata from the drain

Answer 1

Correct Answer - Option 2 : coefficient of permeability of the soil to be drained

Explanation:

• Tile drainage is a type of drainage system that removes excess water from soil below the surface.
• Plants need air as well as moisture in their root zones for their survival, excess irrigation farm water is free to move into underground tile drains.
• This water if not removed retards the plant growth because it fills the soil voids and restricts proper aeration, therefore there is a need for sub-surface drainage or tile drainage.

Spacing of the tile drainage is given by,

\(S = \frac{{4K}}{q}\left( {{b^2} - {a^2}} \right)\)

Where K = Coefficient of permeability

q = Discharge per unit length in the drain

a = Depth of the impervious strata below the drain

b = Maximum height of the drained water table above the impervious layer.

So, from the above equation, it is clear that spacing of tile drains to relieve water-logged land is directly proportional to the coefficient of permeability of the soil to be drained