Seismic Performance of Circular Tunnels Considering Soil–Structure Interaction and Earthquake Intensity

Underground tunnels are often considered less vulnerable to seismic loading than surface structures; however, strong earthquakes have shown that significant damage may occur depending on soil conditions and earthquake characteristics. This study investigates the dynamic response of a circular underground tunnel subjected to strong ground motions using time-history numerical analysis. A two-dimensional plane-strain model of the coupled soil–tunnel system is developed, in which nonlinear hysteretic soil behavior is simulated using the UBCHYST constitutive model, while the tunnel lining is modeled as a linearly elastic structure with reduced stiffness to represent segmental joints. Dynamic analyses are performed using earthquake input motions with different peak ground acceleration (PGA) levels to evaluate the influence of earthquake amplitude on tunnel and ground response. The seismic performance is assessed in terms of ground surface settlement, effective stress variation, acceleration response, and internal forces in the tunnel lining. The results show that increasing PGA significantly amplifies ground settlement and bending moment demand in the tunnel lining, while axial force response is less sensitive to earthquake amplitude. In addition, the presence of the tunnel modifies the dynamic characteristics of the soil mass and reduces the natural frequency of the system. These findings highlight the importance of considering nonlinear soil behavior and soil–structure interaction in seismic assessment of underground tunnels.

کلیدواژه ها:

Underground tunnel ، Seismic response ، Soil–structure interaction ، Dynamic time-history analysis