GATE 2017 CE (CE2) – Question 31
A sheet pile penetrates 12 m into a homogeneous isotropic soil with hydraulic conductivity $10^{-6}$ m/s. Head difference across the pile is 4 m. The flow net has 5 flow lines and 11 equipotential lines. Seepage per metre length of pile, to one decimal place, is ______ cm³/s.
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Correct answer: 1.6 to 1.6
Explanation
Count spaces between lines: five flow lines give four channels, and eleven equipotential lines give ten drops. Seepage per metre is $$q=kH\frac{N_f}{N_d}=10^{-6}(4)\frac4{10}=1.6\times10^{-6}\ \mathrm{m^3/s}.$$ Convert using one million cm³ per m³: 1.6 cm³/s per metre.