Analytical solution for longitudinal responses of tunnels under combined effects of seismic waves and strike-slip faulting
Jie Tang, Manchao He, Yafei Qiao, Hanbing Bian, Chun Zhu
Abstract
Strong seismic excitation and fault dislocation are likely to occur simultaneously in high-intensity seismic zones, causing severe damage to tunnels crossing active fault zones. This paper aims to develop a novel analytical solution to determine the longitudinal mechanical responses of tunnels subjected to the combined effects of seismic waves and strike-slip faulting. Adopting the elastic spring-beam model, the seismic waves are modelled as shear horizontal (SH) waves and the fault dislocation follows an S-shaped pattern; the superposition principle for free-field displacements caused by both effects is assumed. In addition, the transmission and reflection of seismic waves at the fault-rock geological interface and the tangential contact conditions at the tunnel-rock interface are considered. The analytical model is validated against numerical simulations, confirming its accuracy in calculating tunnel responses. Moreover, a parametric study is conducted to evaluate the impact of key factors, including fault displacement, fault zone width, fault dip angle, earthquake frequency, rock conditions, tunnel lining stiffness, and tangential contact conditions, on tunnel responses. Compared with each effect alone, the combined effects of seismic waves and strike-slip faulting significantly change the tunnel deformation and internal forces, leading to increased tunnel responses, especially within the fault zone and near the fault-rock interfaces. Depending on specific parameters, tunnel responses can be classified into seismic-dominated, faulting-dominated, and seismic-faulting coupled responses on the basis of the relative contributions of each effect. The proposed analytical solution can be applied to quickly predict the longitudinal mechanical behaviour of tunnels under such combined effects in engineering applications.