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<p>In the process of significant deformation in soft rock tunnels, it is crucial to clarify the mechanical laws governing the surrounding rock to propose effective support measures, ensuring the safety of the tunnel during both pre-construction and subsequent operations. This study first analyzes statistics of large deformation disasters from M tunnel, revealing that part of the rock mass exhibits characteristics of unloading expansion during the excavation of a soft rock tunnel. Subsequently, the impact of the maximum horizontal principal stress and the mechanical properties of the surrounding rock on its deformation and the stability of the supporting structure is examined through numerical simulations. Finally, a yield support system incorporating a Polyurethane (PU) foam energy absorbing buffer layer to manage significant deformation in soft rock tunnels is proposed. The results are as follows: adjusted the elastic moduli dynamically of the surrounding rock during loading and unloading in the numerical simulation, can accurately reflect the unloading expansion characteristics of the surrounding rock. This result is also verified by the field monitoring data. With the increase of the angle between the maximum horizontal principal stress and the tunnel axis, the initial support structure shows an obvious bottom slab crack. The deterioration of the surrounding rock will lead to an increase in the deformation of the arched roof and the inverted arch. When the load is 2.0&#xa0;MPa, cracks appear in the conventional rigid support system. However, the yielding support system with its energy-absorbing and pressure-relieving characteristics remains stable even when the load is 8.0&#xa0;MPa. The PU foam energy-absorbing buffer layer can effectively control the continuous deformation of the soft rock tunnel, significantly reduces the stress on the secondary lining structure and makes the stress distribution more uniform. The stress distribution is more uniform, which improves the overall performance of the supporting structure system. This feature is significant in ensuring the safety of soft rock tunnel construction and operation.</p>

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Study on Evaluation and Control Measures of Large Deformation of Soft Rock Tunnels Considering Unloading Physical Expansion

  • 期刊论文

  • 发表日期：

    2025年1月28日

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  • Junfu Fu,
  • Jimeng Feng,
  • Bin Li,
  • Junru Zhang,
  • Hui Jiang,
  • Yangfan Wu

摘要

In the process of significant deformation in soft rock tunnels, it is crucial to clarify the mechanical laws governing the surrounding rock to propose effective support measures, ensuring the safety of the tunnel during both pre-construction and subsequent operations. This study first analyzes statistics of large deformation disasters from M tunnel, revealing that part of the rock mass exhibits characteristics of unloading expansion during the excavation of a soft rock tunnel. Subsequently, the impact of the maximum horizontal principal stress and the mechanical properties of the surrounding rock on its deformation and the stability of the supporting structure is examined through numerical simulations. Finally, a yield support system incorporating a Polyurethane (PU) foam energy absorbing buffer layer to manage significant deformation in soft rock tunnels is proposed. The results are as follows: adjusted the elastic moduli dynamically of the surrounding rock during loading and unloading in the numerical simulation, can accurately reflect the unloading expansion characteristics of the surrounding rock. This result is also verified by the field monitoring data. With the increase of the angle between the maximum horizontal principal stress and the tunnel axis, the initial support structure shows an obvious bottom slab crack. The deterioration of the surrounding rock will lead to an increase in the deformation of the arched roof and the inverted arch. When the load is 2.0 MPa, cracks appear in the conventional rigid support system. However, the yielding support system with its energy-absorbing and pressure-relieving characteristics remains stable even when the load is 8.0 MPa. The PU foam energy-absorbing buffer layer can effectively control the continuous deformation of the soft rock tunnel, significantly reduces the stress on the secondary lining structure and makes the stress distribution more uniform. The stress distribution is more uniform, which improves the overall performance of the supporting structure system. This feature is significant in ensuring the safety of soft rock tunnel construction and operation.