Impact of Discontinuities with Slip-Weakening Friction on the Structural Deformation of a High-Speed Railway Tunnel inJointed Stratified Rock Masses Under Cyclic Train Loadings

Abstract

ABSTRACT It is crucial to assess the performance of a high-speed railway tunnel under dynamic train loading since structural deformations may lead to safety-relevant issues, such as train derailment or rollover. The structural deformation of a high-speed railway tunnel results from the train loading-induced response and interaction of tunnel structures and surrounding rock masses. Our research investigates the slippage behavior of discontinuities with slip-weakening friction around a tunnel under dynamic train loadings, and further analyzes their impacts on structural deformations. A distinct element method-based commercial software (UDEC) is used to build a 2D circular tunnel situated in jointed stratified rock masses. We compare the modeling results by the Coulomb slip model and slip-weakening model, and further conduct parametric studies about the bedding plane dip angle, joint length/spacing, and critical slip distance. We report that discontinuities with slip-weakening friction are more prone to be reactivated and ruptured under dynamic train loadings, and the resultant shear displacements of discontinuities associated with rock block deformations and movements would further induce significant structural deformations. Our simulation results have important implications for assessing the performance of a high-speed railway tunnel as well as the safety of train operations. INTRODUCTION The rapid development of high-speed railways in China, e.g., the planned Sichuan-Tibet railway line, imposes an increased demand of tunnel construction (Li et al. 2016). Due to the high performance requirements of high-speed train operation, the structural deformation of a tunnel should be carefully examined and controlled to ensure the safety and smoothness of train tracks (Fu et al. 2022; Qian et al. 2019). Some considerable structural deformations have been observed under dynamic train loadings (Wang et al. 2022), as a result of the interaction of tunnel structures and surrounding rock masses (Wang et al. 2020). Discontinuities are widely present in rock masses like stratified sedimentary formations, a typical lithology through which parts of the Sichuan-Tibet railway pass (Chen et al. 2019; Guo et al. 2020). It is expected that the potential shear slippage of these discontinuities under dynamic train loadings could play an important role in structural deformations.