Exercice $2$:

We need to design a circular duct of $7$ m diameter $($measured at mid thickness of the duct$)$; this duct is subjected to a water charge of $6\mathrm{.}5$ m $.$ It rests on a continuous cradle with an angle of $70.$ The duct is not subjected to backfilling or overloading.

Given: $fc=350K\frac{g}{c}{m}^2,$ fs $=1200K\frac{g}{c}{m}^2,$ Water density $=1000k\frac{g}{m^3},$ Thickness of the pipe $=0\mathrm{.}3m$; Concrete density $=2500K\frac{g}{m^3}$