Dynamic seismic response of shallow-buried rectangular underground passages constructed using the pipe-roof preconstruction method

Shallow-buried underground passages constructed using the pipe-roof preconstruction method (PPM) are widely applied in densely populated urban areas to control ground deformation during excavation. However, the seismic response characteristics of such composite underground structural systems remain insufficiently documented, particularly in soft-ground environments. This study investigates the seismic behavior of a shallow-buried rectangular underground passage constructed using the PPM technique through three-dimensional dynamic finite element analysis. A detailed numerical model was developed using PLAXIS 3D to simulate staged construction processes and dynamic soil – structure interaction under earthquake loading. The Hardening Soil model with small-strain stiffness (HSS) was adopted to represent nonlinear soil behavior. Bidirectional seismic excitation was applied to evaluate deformation characteristics and structural response. The numerical results indicate that ground deformation and structural displacement are strongly influenced by the direction of seismic input. Larger deformation responses occur in the direction consistent with the applied ground motion, while structural interfaces and corner regions tend to experience higher internal force demand. The seismic response of the underground passage is governed by the combined effects of soil dynamic properties and structural stiffness distribution. The findings provide case-based engineering insights into the seismic response characteristics of PPM-supported underground passages constructed in soft-ground urban environments.