<p>Time-dependent failure in deep-buried pressurized tunnels involves complex tensile–shear transitions within the rock–support composite system, yet the internal pressure dependency remains poorly understood. This study conducted physical model experiments simulating tunnels under extreme stress (burial depth: 2525 m) with controlled internal pressure levels (0–300 kPa). Integrating acoustic emission (AE) and digital image correlation (DIC) monitoring, we quantified time-dependent damage evolution from microcrack nucleation to macrofracture coalescence. Key findings include: (1) Elevated internal pressure (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">${P}_{i}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>P</mi> <mi>i</mi> </msub> </math></EquationSource> </InlineEquation>) delays failure onset but amplifies collapse severity, increasing peak strength according to the relation <InlineEquation ID="IEq2"> <EquationSource Format="TEX">${\sigma }_{peak}=0.0133{P}_{i}+23.71$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>σ</mi> <mrow> <mi mathvariant="italic">peak</mi> </mrow> </msub> <mo>=</mo> <mn>0.0133</mn> <msub> <mi>P</mi> <mi>i</mi> </msub> <mo>+</mo> <mn>23.71</mn> </mrow> </math></EquationSource> </InlineEquation> MPa. (2) Internal pressure drives a tensile-to-shear transition, characterized by shear fracture proportion rising from 52.49 (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">${P}_{i}=0$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>P</mi> <mi>i</mi> </msub> <mo>=</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>) to 73.91% (<InlineEquation ID="IEq4"> <EquationSource Format="TEX">${P}_{i}=300$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>P</mi> <mi>i</mi> </msub> <mo>=</mo> <mn>300</mn> </mrow> </math></EquationSource> </InlineEquation> kPa), which shifts failure from brittle spalling to ductile shear-band formation. (3) AE diagnostics reveal two precursory indicators of catastrophic instability, characterized by a sharp reduction in b-value (> 70% drop) and a significant increase in shear fracture proportion (> 50–70% in this specific material). This study establishes internal pressure as a critical factor of failure mechanisms in deep-buried pressurized tunnels, contributing to a deeper understanding of their long-term performance and thereby informing principles of tunnel design, operation, and maintenance.</p>

Internal Pressure Drives Tensile-to-Shear Transition in Time-Dependent Failure of Deep-Buried Pressurized Tunnels: An AE–DIC Physical Modeling

期刊论文
发表日期：

2025年10月22日

查看全文

Xiang Huang,
Shaojun Li,
Guoqiang Zhu,
Dingping Xu,
Zejie Feng

摘要

Time-dependent failure in deep-buried pressurized tunnels involves complex tensile–shear transitions within the rock–support composite system, yet the internal pressure dependency remains poorly understood. This study conducted physical model experiments simulating tunnels under extreme stress (burial depth: 2525 m) with controlled internal pressure levels (0–300 kPa). Integrating acoustic emission (AE) and digital image correlation (DIC) monitoring, we quantified time-dependent damage evolution from microcrack nucleation to macrofracture coalescence. Key findings include: (1) Elevated internal pressure ( ${P}_{i}$ $P_{i}$ ) delays failure onset but amplifies collapse severity, increasing peak strength according to the relation ${\sigma }_{peak}=0.0133{P}_{i}+23.71$ $σ_{peak} = 0.0133 P_{i} + 23.71$ MPa. (2) Internal pressure drives a tensile-to-shear transition, characterized by shear fracture proportion rising from 52.49 ( ${P}_{i}=0$ $P_{i} = 0$ ) to 73.91% ( ${P}_{i}=300$ $P_{i} = 300$ kPa), which shifts failure from brittle spalling to ductile shear-band formation. (3) AE diagnostics reveal two precursory indicators of catastrophic instability, characterized by a sharp reduction in b-value (> 70% drop) and a significant increase in shear fracture proportion (> 50–70% in this specific material). This study establishes internal pressure as a critical factor of failure mechanisms in deep-buried pressurized tunnels, contributing to a deeper understanding of their long-term performance and thereby informing principles of tunnel design, operation, and maintenance.