عنوان مقاله [English]
During construction of underground openings, such as: tunnels, shafts and caverns stress concentrations increase near these openings and instability problem occur in these underground excavations. Tests on thick-walled hollow cylinders of rock are a relatively easy, economical and realistic means to better understand stability and the mechanisms associated to underground openings failure. The mode of rupture observed in the tests was a pair of radial rupture planes. These rupture planes correspond to a compacting failure mechanism, because, these planes are perpendicular to major principal stress (tangential stress). This kind of rupture usually occurs in very porous material.