چكيده به لاتين
Recent powerful earthquakes have highlighted the importance of understanding how underground structures react during seismic events. The damage observed emphasizes the need to assess the vulnerability of these structures to minimize potential damage in future quakes.
The design of a tunnel, including its shape and size, is driven by its intended use, the excavation method employed, and the chosen approach for long-term upkeep. When feasible, opting for a design that minimizes overall construction costs is ideal.
This study focuses on how the shape of a tunnel section impacts its performance during earthquakes. We began by examining existing methods for analyzing the seismic behavior of underground structures and reviewed research on fragility curves, which assess a structure's vulnerability to earthquakes. Following this review, we employed a numerical technique called dynamic time history analysis to evaluate three different tunnel shapes: circular, square, and horseshoe. This analysis used the principle of maximum likelihood for data validation.
We utilized Abaqus finite element software to analyze and validate the models. The tunnels were subjected to seismic loads derived from the accelerograms of 37 earthquakes. To assess damage, we defined levels based on the ratio of bending moment and axial force obtained from the analysis. Finally, fragility curves were generated using a probabilistic method to illustrate the seismic vulnerability of each tunnel section across all damage levels.
The analysis revealed that square and circular tunnels exhibited the highest and lowest vulnerability, respectively, when the fragility curve was based on bending moment damage. Conversely, when the curve considered axial force, the circular tunnel showed the greatest potential for damage due to experiencing the highest maximum axial force. Interestingly, the peak acceleration within the tunnel walls displayed minimal dependence on the tunnel geometry across the earthquake records, suggesting that the amplification ratio is relatively consistent for all three shapes.
