3D response analysis of tunnels in layered media subjected to asynchronous ground motions using MLM-DRM

Abstract

Underground tunnels are crucial parts of modern urban infrastructure and are used for a wide range of applications worldwide. Tunnels situated in layered soil media respond differently to seismic loads compared to surface structures. Historically, earthquakes have caused major damage to tunnels, including cracks in the lining, joint separation, leaks, and even collapse. Most previous studies have focused on the plane strain response of tunnels. However, these 2D analyses cannot explain the 3D deformation patterns seen in tunnels near earthquake faults or scenarios where the properties of the tunnel/soil, or the seismic wavefield, vary along the tunnel axis. Factors such as wave passage effects, layered geology, and fault inclinations greatly impact the dynamic response of tunnels during earthquakes. To address these issues, a more accurate and robust approach involving asynchronous excitation is necessary to account for the spatial variability of seismic forces. A Multi-Layer Modified Domain Reduced Method (MLM-DRM) is extended in this study, which reduces computational time and cost while maintaining high modeling accuracy. Three tunnel cross-sections at different locations in layered media are analyzed to show how variations in geometric and geotechnical parameters affect seismic performance. The von Mises stress distribution around the tunnel circumference is examined at various time steps to observe transient stress evolution. Response spectra are evaluated at different locations of tunnel circumference. The results highlight the significance of geological stratification, spatial wave propagation, and fault inclination in determining tunnel behavior under seismic loads, providing essential insights for advancing seismic design practices that enhance tunnel resilience, operational safety, and serviceability during and after earthquakes.