Dynamic response analysis of prestressed segmental utility tunnels in non-uniform soil under obliquely incident seismic waves

Abstract It is widely acknowledged that monolithic in situ underground utility tunnels possess exceptional seismic resilience. Conversely, prefabricated integrated tunnels, marked by multiple joints and compromised integrity, face seismic challenges due to unclear damage mechanisms in non-uniform soil under earthquakes with varied incident angles. Leveraging shaking table test results of scaled models, this paper introduces an oblique incidence viscoelastic boundary input method for Auto_VSB and establishes a nonlinear seismic analysis model for prestressed prefabricated tunnels, validating their seismic response in uniform soil. The study compares dynamic responses between uniform and non-uniform soil sites under oblique seismic waves, revealing seismic response and damage patterns. Compared to vertical incidence, oblique waves significantly amplify soil base accelerations, boosting the vertical acceleration amplification factor and causing increased vertical joint displacements. During a 0.6 g peak acceleration earthquake, tunnels in uniform soil remained intact, while those in non-uniform soil showed significant deformation and plastic failure. Maximum tensile stress occurred at the middle corridor joint’s top, with excessive joint opening, identifying it as a critical area. Therefore, in practical engineering, special focus should be on the vertical impact of oblique seismic waves on structures. The research findings provide valuable insights for analyzing the seismic performance of utility tunnels.