ASSIGNMENT PROBLEM $1(5$ marks$)$ A circular tunnel will be constructed in gabbro at a depth of $1,100$ m below the ground level. For the rock consider that there are two joint sets, the joints are planar and smooth and that the rockwall contact has only silty coating with small clay fraction. If the UCS for the rock is $180$ MPa and RQD was evaluated as $70\%,$ examine if the rock will fail during the excavation of the tunnel. Consider that the lateral normal stress during excavation will become equal to zero and that the constant D is equal to $0\mathrm{.}15.$ During the excavation of the tunnel, dry conditions are considered. In the absence of more specific information needed, make some assumptions and$/$or use $$average$$ design parameters.