There is a tunnel $12$ m below ground surface. A water tank and a rectangular foundation for a building is planned to

be constructed on the ground surface at the location as shown in Figure $2($Plan view$).$ The $18$ m diameter water tank

will impose $70$ kPa stress $($Including tank self$-$weightplus water pressure$)$ and the rectangular foundation will distribute

$30$ kPa stress on the ground surface. What will be the stress increase due to these two constructions at point C $,$ at

the tunnellevel that is $12$ m below ground surface?

Use graphical methods to find stress increase