Underground structures are exposed to stability issues associated with roof collapse, both during their construction and operation. A major source of uncertainties in tunnels’ roof stability come from the behavior of rock or soil. The Hoek-Brown yield criterion is typically used in analyses when tunnels are constructed in rocks, but in soils and soft rocks the Mohr-Coulomb criterion is more often utilized. However, the tensile strength following from the Mohr-Coulomb criterion may be unrealistic. For that reason, a tension cutoff is proposed, which truncates the yield surface in tensile regime. An analysis of tunnel roof stability in geomaterial with tension cutoff is described in this paper. The kinematic approach of limit analysis is used. Introducing tensile strength cutoff produces nonlinearity in the strength envelope, promoting a multiplicity of admissible roof failure patterns. Stability numbers for an unsupported roof are calculated and support stress is derived that assures stability.

LOKASI: Ruang Koleksi Umum
Rak: 2