A long drain pipe is installed below ground as shown in the figure below. The flow net

for the steady stage seepage from the ground surface to the pipe during a rain fall is

shown in the figure. The soil is a silty sand having a coefficient of permeability of $5\mathrm{.}2$

${10}^{-5}\frac{m}{s}$ and a total unit weight of $18\mathrm{.}5k\frac{N}{m^3}.$

a$)$ What is the vertical effective stress in the soil at Point $x?$

b$)$ At what rate, in $\frac{m^3}{s}$ per metre run of the pipe, does the pipe collect the rainwater

seepage?

Answer: a$)49\mathrm{.}61$ kPa and b$)1\mathrm{.}66\backslash$times $10-4$ m$3/$s pmr