Question

A 800 m${}^3$/day of water drawn from a proposed infiltration gallery which is placed at 8 m depth in the bank of the river. The coefficient of permeability of soil aquifer is 100 m/day, then the length of gallery (in m) if the draw down in the gallery on pumping is not to exceed 4 m. (Take the radius of influence as 100).

• A. 33.33
• B. 19.81
• C. 15.36
• D. 39

Answer 1

The correct option is A 33.33

$Q=800m^3/day$

$H=8m$

$K=100m/day$

$L=?$

$h=H-S=8-4=4$

$R=100m$

$\therefore$ Infiltration gallery is constructed in the bank it collects only water form one side

$Q=\frac{KL(H^2-h^2)}{2R}$

$800=\frac{100\times L(8^2-4^2)}{2\times 100}\Rightarrow L=33.33m$