Underground excavations are of immense interest to mining engineers worldwide. Underground projects are often complex in nature where geological features, geomechanical parameters of rock mass and stress play important role. The present research has conducted 2D, Quasi-3D and 3D continuum analyses of the underground excavation of the extension phase at the Masjed-e-Solaiman hydroelectric project inIran’s southwesternprovince ofKhuzestan. The effects of weak zones and the formation of multiple openings in the inhomogeneous rock mass have, in particular, been taken into account during those analyses. This study reveals that 2D is more deformed than the other models, whereas 3D analysis yields the best results comparable with in-situ measurements.