Study of Mechanical Response of Tunnels Crossing Active Faults in Different Burial Depths

There are numerous tunnels worldwide that cross active fault zones. These tunnels are situated in complex geological environments and are subjected to intense seismic activities. When active fault zones experience displacement, tunnels are susceptible to varying degrees of damage. Over the past few decades, many scholars have researched tunnels crossing active fault zones using numerical simulation methods, including finite element analysis, discrete element analysis, and finite difference methods. However, certain aspects have been overlooked, such as the influence of burial depth on tunnels crossing active fault zones. Most prior studies have primarily omitted consideration of tunnel depth and high-stress effects, resulting in disparities between research findings and practical engineering outcomes. In light of these issues, this paper analyzes the impact of ground stress fields at different burial depths on tunnels crossing active fault zones. It compares the mechanical response characteristics of deep-buried and shallow-buried tunnels after experiencing fault displacement, elucidating variations in displacement patterns, stress, and strain at different burial depths. The results indicate that: (1) Deep-buried and shallow-buried tunnels exhibit an “S”-shaped deformation pattern. (2) Regarding the strain distribution within the tunnel, the affected regions are predominantly concentrated within the fault zone. (3) Regarding the stress distribution within the tunnel, deep-buried tunnels experience a broader range of stress variations distributed across the fault zone. In contrast, shallow-buried tunnels predominantly exhibit stress concentration at the fault slip plane. (4) By analyzing the patterns of tunnel damage at different burial depths, it is observed that burial-depth effects notably influence tunnels with a burial depth less than 200 m. In comparison, tunnels exceeding 300 m gradually reduce the impact of burial depth. These findings can be essential theoretical references for studying tunnels crossing active fault zones in deep-buried environments.

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