<p>Leakage at tunnel structural joints represents a critical vulnerability in tunnel waterproofing systems. The interaction between secondary lining cavity development and waterproofing system failure creates a vicious cycle that accelerates tunnel structural joint leakage instability risks. Forty physical model tests were conducted to investigate and quantify the impacts of cavity depth, dimension, and spatial distribution on joint leakage under varying hydraulic heads. The study employed a self-developed tunnel lining leakage defect simulation apparatus. Experimental investigation elucidates the coupled hydro-mechanical mechanisms governing seepage evolution and stress redistribution in defective lining structures. Key findings indicate that water pressure progressively accumulates at the lining with increasing hydraulic head height, while cavity zones maintain consistently lower pressure due to pressure relief effects. This pressure distribution causes the water pressure sharing ratio <i>η</i> to increase with higher head height, while gradually decreasing as cavity breakage becomes more severe. Cavity extent expansion demonstrates the most significant influence, decreasing vault earth pressure by 23.8% compared to 15.8% and 19.5% reductions from depth extension and spatial redistribution. Cavity depth expansion resulted in a 25.4% increase in the axial force at the vault, along with a 3-fold increase in the bending moment. Expansion of the cavity extent mainly led to a 40.3% increase in axial force and a 1.8-fold increase in bending moment. These findings provide quantitative insights for optimizing waterproofing design and developing targeted maintenance strategies for cavity-affected tunnel structures.</p>

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Influence of lining cavity characteristics on structural joint leakage behavior in urban tunnels

  • Pengfei Li,
  • Yi Li,
  • Qing Xu,
  • Junjie Zeng,
  • Sulei Zhang

摘要

Leakage at tunnel structural joints represents a critical vulnerability in tunnel waterproofing systems. The interaction between secondary lining cavity development and waterproofing system failure creates a vicious cycle that accelerates tunnel structural joint leakage instability risks. Forty physical model tests were conducted to investigate and quantify the impacts of cavity depth, dimension, and spatial distribution on joint leakage under varying hydraulic heads. The study employed a self-developed tunnel lining leakage defect simulation apparatus. Experimental investigation elucidates the coupled hydro-mechanical mechanisms governing seepage evolution and stress redistribution in defective lining structures. Key findings indicate that water pressure progressively accumulates at the lining with increasing hydraulic head height, while cavity zones maintain consistently lower pressure due to pressure relief effects. This pressure distribution causes the water pressure sharing ratio η to increase with higher head height, while gradually decreasing as cavity breakage becomes more severe. Cavity extent expansion demonstrates the most significant influence, decreasing vault earth pressure by 23.8% compared to 15.8% and 19.5% reductions from depth extension and spatial redistribution. Cavity depth expansion resulted in a 25.4% increase in the axial force at the vault, along with a 3-fold increase in the bending moment. Expansion of the cavity extent mainly led to a 40.3% increase in axial force and a 1.8-fold increase in bending moment. These findings provide quantitative insights for optimizing waterproofing design and developing targeted maintenance strategies for cavity-affected tunnel structures.