부산대학교 도서관

This research investigates the utilization of tunnel junctions in underground design, focusing on accessibility, connectivity, and safety considerations. The study specifically examines tunnel junctions within hydropower tunnels in eastern Nepal, employing the Rocscience Phase2 finite element model (FEM) with a post-peak failure approach. The generalized Hoek–Brown method, complemented by the strain-softening method and incorporating the residual Geological Strength Index (GSI) proposed by Cai et al. (Int J Rock Mech Min Sci 44:247–265, 2007), is applied in the model. The resulting analysis encompasses volumetric strain, shear strain, and stress distribution, facilitating the comprehensive evaluation of tunnel intersections, corroborated by on-site geological verification. Findings indicate a direct correlation between stress distribution in tunnels, overburden increments, and tunnel openings for specific pillar dimensions, as vertical stress is inherently tied to overburden. Smaller pillars exhibit heightened vulnerability to increasing overburden and excavation sequences, with notable impacts extending to the periphery of the pillar section. Moreover, the study underscores that 2D numerical modeling, using software such as Phase2, falls short in illustrating stress unloading commonly associated with conventional drill blast excavation methods. As a recommendation, the adoption of other explicit or implicit FEM models capable of accurately capturing dynamic unloading and failure conditions is advised. Ultimately, a comprehensive understanding of the stress path proves imperative in ensuring the effective performance of project components within the desired factor of safety.