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<p>Soft rock tunnels face serious long-term stability challenges arising from time-dependent deformation, moisture-induced strength degradation, and progressive deterioration of supporting structures. Although the timing of support installation is critical for mitigating these effects, conventional practices rely heavily on empirical judgment and lack a unified framework that couples rock rheology with support degradation. This study develops a time-resolved methodology to optimize primary support and secondary lining application timing. A creep-based failure criterion is established using a Burgers-Drucker-Prager model with moisture-dependent strength parameters. A time-dependent self-bearing coefficient characterizes surrounding rock stability evolution; its nonlinear equation’s unique positive root defines the critical primary support timing (hours). For secondary lining, a degradation-damage interaction model quantifies the time-varying bearing capacity of shotcrete, steel ribs, and anchors. Optimal timing occurs when external load reaches 80% of this capacity. Parametric analyses show increasing moisture content (0% to 12%) shortens critical primary support timing by up to 62%, while a larger dilation angle delays primary support but accelerates secondary lining need. Numerical simulations demonstrate that inappropriate support timing increases bending moments, axial forces, and reduces safety factors, especially in damaged zones. The proposed framework captures the coupled effects of creep deformation, structural degradation, and stress redistribution, providing a quantitative basis for time-sensitive support scheduling and long-term performance assessment in soft rock tunnels.</p>

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Time-dependent optimization of support application timing in soft rock tunnels considering creep deformation and structural degradation

  • 期刊论文

  • 发表日期：

    2026年5月2日

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  • Hongxiang Zhan,
  • Weijie Dong,
  • Chengyuan Pei,
  • Xiangbo Zhao,
  • Ziquan Chen,
  • Chuan He

摘要

Soft rock tunnels face serious long-term stability challenges arising from time-dependent deformation, moisture-induced strength degradation, and progressive deterioration of supporting structures. Although the timing of support installation is critical for mitigating these effects, conventional practices rely heavily on empirical judgment and lack a unified framework that couples rock rheology with support degradation. This study develops a time-resolved methodology to optimize primary support and secondary lining application timing. A creep-based failure criterion is established using a Burgers-Drucker-Prager model with moisture-dependent strength parameters. A time-dependent self-bearing coefficient characterizes surrounding rock stability evolution; its nonlinear equation’s unique positive root defines the critical primary support timing (hours). For secondary lining, a degradation-damage interaction model quantifies the time-varying bearing capacity of shotcrete, steel ribs, and anchors. Optimal timing occurs when external load reaches 80% of this capacity. Parametric analyses show increasing moisture content (0% to 12%) shortens critical primary support timing by up to 62%, while a larger dilation angle delays primary support but accelerates secondary lining need. Numerical simulations demonstrate that inappropriate support timing increases bending moments, axial forces, and reduces safety factors, especially in damaged zones. The proposed framework captures the coupled effects of creep deformation, structural degradation, and stress redistribution, providing a quantitative basis for time-sensitive support scheduling and long-term performance assessment in soft rock tunnels.