Mechanical response and failure characteristics of tunnels subjected to reverse faulting with nonuniform displacement: Theoretical and numerical investigation

Abstract

Tunnels subjected to reverse fault dislocation undergo severe structural damage, and their mechanical response and failure characteristics play a key role in seismic fortification efforts. This paper investigates the mechanical responses and failure characteristics exhibited by tunnels subjected to reverse faulting using theoretical analysis and numerical simulations. A theoretical model is established for analysing the bending moment, shear force, and safety factor of the tunnels under reverse fault dislocation. The nonuniform fault displacement, fault zone width, and nonlinear soil-tunnel interaction is applied in the proposed theoretical model, significantly improving the analysis accuracy and range of applicability. The corresponding numerical simulation based on the XFEM (extended finite element method) is carried out, and the proposed theoretical model is verified by the numerical results. The theoretical results demonstrate excellent agreement with the numerical results when nonuniform fault displacement is considered. A parametric analysis is presented in which the effects of the maximum fault displacement, fault zone width, and ratio of the maximum fault displacement of the footwall to the hanging wall are investigated. The results show that the ultimate fault displacement for compression-bending failure of the tunnel subjected to reverse fault dislocation is estimated to be approximately 30 cm, while the ultimate displacement for shear failure stands at 20 cm. Variations in the fault displacement ratio yield alterations in the distribution pattern and peak values of internal forces, together with shifts in the potential failure ranges of the footwall and hanging wall. Additionally, an initial crack emerged on the tunnel crown near the fault plane, followed by a second crack on the tunnel invert. Upon reaching a fault displacement of approximately 40 cm, the crack fully traverses the entire tunnel lining.