Question

A flownet constructed to determine the seepage through an earth dam which is homogeneous but anisotropic, gave four flow channels and sixteen equipotential drops. The coefficients of permeability in the horizontal and vertical directions are $4.0\times {10}^{-7}m/sand1\times {10}^{-7}m/s$ respectively. If the storage head was 20 m, then the seepage per unit length of the dam (in m3/s) would be

• A. $5\times {10}^{-7}$
• B. $10\times {10}^{-7}$
• C. $20\times {10}^{-7}$
• D. $40\times {10}^{-7}$

Answer 1

The correct option is B $10\times {10}^{-7}$

Seepage is given by

$q=\sqrt{k_x{k}_z}\times \frac{N_f}{N_d}\times H$

$=\sqrt{4\times {10}^{-7}\times 1\times {10}^{-7}}\times \frac{4}{16}\times 20$

$=10\times {10}^{-7}{m}^3/s/m$