Tunnel instability mechanisms in anisotropic rock masses under combined static and dynamic loading

Abstract

In this study, the impact of rock mass anisotropy—arising from the presence and orientation of discontinuities—on tunnel behavior under combined static and dynamic loading was investigated using numerical modeling. The tunnel lining internal force (TLIF) and displacement responses were analyzed by simulating different joint dip angles and in-situ stress ratios through the jointed rock model (JRM). The dynamic loading is applied as a horizontally propagating shear-wave acceleration time history with a peak ground acceleration of 0.3g and dominant frequencies representative of moderate seismic excitation. Results reveal that anisotropy significantly affects stress redistribution and deformation patterns, especially under low stress ratios (K = 0.5) and joint dips around 60°, where bending moments and shear forces can increase by up to 250% relative to the isotropic reference model without discontinuities. In contrast, axial forces and displacements may reduce depending on the joint configuration. The findings provide insight into seismic-induced instability mechanisms in jointed rock masses and help improve understanding of tunnel performance under geohazard-related dynamic loading.

Keywords

Anisotropy / Tunnel lining internal forces / Numerical modeling / Jointed rock model / Static and dynamic loading / Tunnel instability

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