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<p>The overlying excavation has been observed to induce significant deformations in operational tunnels, thereby compromising their structural integrity and safety. Despite the critical nature of this issue, there remains a paucity of well-documented field studies that systematically investigate the evolution of tunnel deformation and the associated challenges, particularly in relation to the efficacy of various treatment measures. This research gap limits the ability to develop effective strategies for ensuring the long-term stability of urban tunnels. To address this gap, this study employed a comprehensive monitoring approach to analyze the entire construction process of an overlying excavation. By integrating field measurements with empirical modeling, the research aimed to characterize the deformation patterns of operational tunnels and evaluate the effectiveness of different treatment strategies. A novel empirical relationship between tunnel heave and the unloading ratio was established using an exponential curve derived from the measured data. The findings revealed that the maximum tunnel heave reached 34.8&#xa0;mm due to the overlying excavation. The tunnel cross-section transitioned from a transverse elliptical shape to a circular configuration as the heave increased. Soil rebound beneath the tunnel and vertical convergence deformation contributed to the heave at the crown, with average proportions of 64% and 36%, respectively. During backfilling and basement grouting, the tunnel heave stabilized, with minor recovery observed after the installation of a dewatering well. A total of 141 tunnel defects, including leakage, concrete cracking, and spalling, were identified, with leakage predominantly observed at circumferential joints and cracking concentrated at the T-joint of the tunnel crown and waist. This study provides a systematic framework for understanding the deformation mechanisms of operational tunnels under overlying excavation. The empirical relationship established between tunnel heave and the unloading ratio offers a valuable tool for predicting tunnel behavior in similar engineering contexts. Furthermore, the insights derived from this research contribute to the development of more effective treatment strategies, thereby enhancing the safety and sustainability of urban tunnel infrastructure.</p>

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Overlying excavation-induced deformation and defects in operating shield tunnels: field measurements and mechanism analysis from a transportation hub

  • 期刊论文

  • 发表日期：

    2025年6月10日

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  • Yuan Liu,
  • Zihan Yang,
  • Hongzhan Cheng,
  • Kai Zhang,
  • Yi Xu,
  • Lv Liu,
  • Renpeng Chen

摘要

The overlying excavation has been observed to induce significant deformations in operational tunnels, thereby compromising their structural integrity and safety. Despite the critical nature of this issue, there remains a paucity of well-documented field studies that systematically investigate the evolution of tunnel deformation and the associated challenges, particularly in relation to the efficacy of various treatment measures. This research gap limits the ability to develop effective strategies for ensuring the long-term stability of urban tunnels. To address this gap, this study employed a comprehensive monitoring approach to analyze the entire construction process of an overlying excavation. By integrating field measurements with empirical modeling, the research aimed to characterize the deformation patterns of operational tunnels and evaluate the effectiveness of different treatment strategies. A novel empirical relationship between tunnel heave and the unloading ratio was established using an exponential curve derived from the measured data. The findings revealed that the maximum tunnel heave reached 34.8 mm due to the overlying excavation. The tunnel cross-section transitioned from a transverse elliptical shape to a circular configuration as the heave increased. Soil rebound beneath the tunnel and vertical convergence deformation contributed to the heave at the crown, with average proportions of 64% and 36%, respectively. During backfilling and basement grouting, the tunnel heave stabilized, with minor recovery observed after the installation of a dewatering well. A total of 141 tunnel defects, including leakage, concrete cracking, and spalling, were identified, with leakage predominantly observed at circumferential joints and cracking concentrated at the T-joint of the tunnel crown and waist. This study provides a systematic framework for understanding the deformation mechanisms of operational tunnels under overlying excavation. The empirical relationship established between tunnel heave and the unloading ratio offers a valuable tool for predicting tunnel behavior in similar engineering contexts. Furthermore, the insights derived from this research contribute to the development of more effective treatment strategies, thereby enhancing the safety and sustainability of urban tunnel infrastructure.