Study of the Bolting of Underground Openings; Calculating Method for Inclined Bolts. | INDAGINE SULLA BULLONATURA DI GALLERIE. METODO DI CALCOLO PER BULLONI COMUNQUE INCLINATI.

The numerical method, previously used by the authors for the stability analysis of underground openings reinforced with rock bolts, is extended in this paper to account for bolts of different orientations with respect to the excavation surface. The state of stress around the bolts is evaluated by using analytical solutions of the Classical Theory of Elasticity. The stresses around the opening, in the rock mass, due to either gravity or tectonic field, are calculated by the Finite Element Method and a model which obeys by the conditions of plane strains. The superimposition of the two stress fields makes it possible to evaluate the stress components around the opening, which can subsequently be used in order to perform stability analyses of the rock structure. Both homogeneous and jointed media can be treated. The numerical results indicate that in a homogeneous rock mass the bolts are effective when properly inclined with respect to the roof opening.