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<p>The creep behavior of soft rock tunnels poses significant challenges to construction safety control. Double-layer primary support (DLPS) systems have gained traction as a leveraging staged construction to optimize stress redistribution and deformation control for deep-buried tunnels in soft rock. Shotcrete serves as the major component in both layers of primary support, yet its hardening feature introduces the complex time-dependent behavior of DLPS. However, age-related properties of the primary support have been overlooked, posing a great challenge to the design and safety control of the DLPS in soft rock tunnels. This paper aims to address this issue by investigating the coupled effects of shotcrete hardening and soft rock rheology on the mechanical interaction between DLPS and soft rock. An analytical model incorporating time-dependent shotcrete properties and rock rheology is established, in which the creep deformation of soft rock is governed by the Burgers model, and the hardening process of shotcrete is simulated by the hypothetical elasticity method. After the correctness of the proposed model has been verified, quantification of the influence of shotcrete hardening on the stress-deformation evolution of DLPS in soft rock tunnels is performed. Results show that the hardening feature directly affects the stress transfer and deformation compatibility between the DLPS and the soft rock. The hardening feature allows for increased tunnel deformation and lower loads carried by supports. The hardening of the first primary support primarily governs rock mass deformation and its load distribution, while the hardening of the second primary support primarily regulates its stress state. Sensitivity analysis of Burgers model rheological parameters is explored, where the reduction in <i>η</i><sub>k</sub> and <i>G</i><sub>m</sub>, as well as the increase in <i>G</i><sub>k,</sub> magnify the impact of the hardening feature on tunnel deformation and stress responses. Finally, the application example highlights the importance of the DLPS parameter selection and combination forms, and demonstrates the design process of the DLSP considering the shotcrete hardening feature and tunnel excavation disturbance. This study aims to provide some insights for the design and optimization of DLPS for soft rock tunnels.</p>

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Time-dependent Mechanical Behavior of Double-Layer Primary Support in Deeply Buried Soft Rock Tunnels Influenced by Hardening Features

  • 期刊论文

  • 发表日期：

    2025年10月3日

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  • Chang Liu,
  • Yunfei Zheng,
  • Sulei Zhang,
  • Dingli Zhang,
  • Mingqing Du,
  • Xiaoming Guan

摘要

The creep behavior of soft rock tunnels poses significant challenges to construction safety control. Double-layer primary support (DLPS) systems have gained traction as a leveraging staged construction to optimize stress redistribution and deformation control for deep-buried tunnels in soft rock. Shotcrete serves as the major component in both layers of primary support, yet its hardening feature introduces the complex time-dependent behavior of DLPS. However, age-related properties of the primary support have been overlooked, posing a great challenge to the design and safety control of the DLPS in soft rock tunnels. This paper aims to address this issue by investigating the coupled effects of shotcrete hardening and soft rock rheology on the mechanical interaction between DLPS and soft rock. An analytical model incorporating time-dependent shotcrete properties and rock rheology is established, in which the creep deformation of soft rock is governed by the Burgers model, and the hardening process of shotcrete is simulated by the hypothetical elasticity method. After the correctness of the proposed model has been verified, quantification of the influence of shotcrete hardening on the stress-deformation evolution of DLPS in soft rock tunnels is performed. Results show that the hardening feature directly affects the stress transfer and deformation compatibility between the DLPS and the soft rock. The hardening feature allows for increased tunnel deformation and lower loads carried by supports. The hardening of the first primary support primarily governs rock mass deformation and its load distribution, while the hardening of the second primary support primarily regulates its stress state. Sensitivity analysis of Burgers model rheological parameters is explored, where the reduction in ηk and Gm, as well as the increase in Gk, magnify the impact of the hardening feature on tunnel deformation and stress responses. Finally, the application example highlights the importance of the DLPS parameter selection and combination forms, and demonstrates the design process of the DLSP considering the shotcrete hardening feature and tunnel excavation disturbance. This study aims to provide some insights for the design and optimization of DLPS for soft rock tunnels.