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<p>Prediction of rock mass plastic zone extension around deep tunnel plays an important role in the design and construction process. The evolution course of plastic zone extent during tunneling subjected to coupling effect of spatial constraint and intermediate principal stress&#xa0;<i>σ</i><sub>2</sub> is investigated in this paper. Based on the unified strength criterion and generalized nonlinear unified strength criterion, an improved solution is proposed by virtual equivalence of spatial constraint for each, respectively. Two representative cases are selected to validate the improved solutions. Two contributing factors to plastic zone extent, including spatial constraint effect and <i>σ</i><sub>2</sub>, are individually analyzed. The underlying mechanism of spatial constraint effect is revealed, while application of convergence–confinement method subjected to spatial constraint effect is subsequently discussed. Results show that constraint effect can extend the classical two-dimensional plane strain solution to three-dimensional one, reflect the dynamic relationship between the extension path and tunneling process. Spatial constraint effect essentially determines the development path of the plastic zone, the convergence–confinement method subjected to this effect can partially explain the deformation issues in soft rock tunnels when tunnel face advancing far away, thus better guiding dynamic design and construction. Intermediate principal stress&#xa0;<i>σ</i><sub>2</sub>&#xa0;restrains the plastic zone extent either, taking no account of which slightly overestimates the upper-limit value for less than 5%. The influence of&#xa0;<i>σ</i><sub>2</sub>&#xa0;behaves weaker than that of spatial constraint effect around tunnel face. Plastic zone obtained by unified strength criterion requires proper estimation of&#xa0;<i>c</i>&#xa0;and&#xa0;<i>φ</i>&#xa0;for rock mass, the average equivalent method by Hoek is suitable for hard rock. However, overestimation of plastic zone may be encountered when being applied in soft rock, calculation direct by generalized nonlinear unified strength criterion can be a good choice in this situation.</p>

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Plastic Zone Extent Around Deep Tunnel Based on Three-Dimensional Strength Criterion Subjected to Spatial Constraint Effect

  • 期刊论文

  • 发表日期：

    2025年9月15日

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  • Yi Yao,
  • Wuwei Zhu,
  • Hongpeng Lai,
  • Hao Li,
  • Yuyang Liu

摘要

Prediction of rock mass plastic zone extension around deep tunnel plays an important role in the design and construction process. The evolution course of plastic zone extent during tunneling subjected to coupling effect of spatial constraint and intermediate principal stress σ2 is investigated in this paper. Based on the unified strength criterion and generalized nonlinear unified strength criterion, an improved solution is proposed by virtual equivalence of spatial constraint for each, respectively. Two representative cases are selected to validate the improved solutions. Two contributing factors to plastic zone extent, including spatial constraint effect and σ2, are individually analyzed. The underlying mechanism of spatial constraint effect is revealed, while application of convergence–confinement method subjected to spatial constraint effect is subsequently discussed. Results show that constraint effect can extend the classical two-dimensional plane strain solution to three-dimensional one, reflect the dynamic relationship between the extension path and tunneling process. Spatial constraint effect essentially determines the development path of the plastic zone, the convergence–confinement method subjected to this effect can partially explain the deformation issues in soft rock tunnels when tunnel face advancing far away, thus better guiding dynamic design and construction. Intermediate principal stress σ2 restrains the plastic zone extent either, taking no account of which slightly overestimates the upper-limit value for less than 5%. The influence of σ2 behaves weaker than that of spatial constraint effect around tunnel face. Plastic zone obtained by unified strength criterion requires proper estimation of c and φ for rock mass, the average equivalent method by Hoek is suitable for hard rock. However, overestimation of plastic zone may be encountered when being applied in soft rock, calculation direct by generalized nonlinear unified strength criterion can be a good choice in this situation.