Seismic vulnerability assessment and fragility analysis of tunnels in Oman: Development of risk matrices and functionality guidelines

Abstract

Past seismic events worldwide inflicted severe damage on tunneling and underground infrastructure projects and resulted in considerable socioeconomic loss. In this study, the seismic vulnerability of tunnels in the Sultanate of Oman is assessed, accounting for tunnel typology and localized site conditions. Seismic Fragility Curves (SFCs) were developed for two seismic zones (Zone 1 and Zone 2) based on the proposed intensity-response relationship, incorporating two different lining properties. Results consistently indicated a 39.56 % decrease in raking ratio for every 15 m/s reduction in shear wave velocity (VSST) across all tunnel models, spanning soft to stiff strata conditions. Employing the fragility functions developed for the Sultanate of Oman, project-specific risk matrices and operational route maps for Al-Sharqiyah Expressway Tunnel-2 (AST2) were formulated, along with an assessment of post-seismic operational accessibility. The insights garnered from this investigation provide fundamental guidance for engineers, designers, and consultants involved in seismic analysis and design of underground structures, encompassing both new constructions and retrofitting endeavors. Furthermore, the data generated herein offers valuable input for governmental stakeholders, facilitating policy formulation and the establishment of national-level design directives concerning tunneling projects within the Sultanate of Oman.