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<p>In the loess strata, which has unique engineering characteristics, the new tunnel excavation can easily damage the adjacent tunnel lining. So, proposing effective reinforcement measures for the existing tunnel’s safe operation is particularly significant. Relying on the project of Yan’ an No.1 Tunnel of Yanyu Railway adjacent to an existing Baotashan Tunnel, this article first carried out the triaxial compression test on clay loess and sandy loess under different water content to explore their failure modes and mechanical properties. Subsequently, the influence of new tunnel excavation on the existing tunnel lining under three kinds of loess water content was analyzed by numerical simulation. Finally, the reinforcement effect, the optimal layout spacing and length of concrete-filled steel tube (CFST) piles were studied. It was found that the failure modes of the two loess at different water content are producing large plastic deformation, and their shear strength declines with the increment of water content. Excavating the new tunnel causes extra deformation and stress to the existing tunnel lining. The higher the water content of loess, the greater the extra deformation and stress. When CFST piles are used to reinforce the stratum, the existing tunnel lining’s deformation and stress are significantly reduced. Considering the economy and the reinforcement effect, when the water content of loess is 8%, 14%, and 20%, respectively, the spacing of CFST piles is 1.6&#xa0;m, 1.2&#xa0;m, and 1.2&#xa0;m, and the length is 25 m, 25 m, and 30 m, respectively.</p>

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Construction Impact of a New Tunnel Adjacent to an Existing Tunnel and CFST Pile Reinforcement in Loess Strata

  • 期刊论文

  • 发表日期：

    2025年6月24日

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  • Jiahao Chen,
  • Shengtao Wang,
  • Junru Zhang,
  • Junfu Fu,
  • Ying Xiong,
  • Ziyan Fan,
  • Zhaojiu Li,
  • Wenyin Zheng

摘要

In the loess strata, which has unique engineering characteristics, the new tunnel excavation can easily damage the adjacent tunnel lining. So, proposing effective reinforcement measures for the existing tunnel’s safe operation is particularly significant. Relying on the project of Yan’ an No.1 Tunnel of Yanyu Railway adjacent to an existing Baotashan Tunnel, this article first carried out the triaxial compression test on clay loess and sandy loess under different water content to explore their failure modes and mechanical properties. Subsequently, the influence of new tunnel excavation on the existing tunnel lining under three kinds of loess water content was analyzed by numerical simulation. Finally, the reinforcement effect, the optimal layout spacing and length of concrete-filled steel tube (CFST) piles were studied. It was found that the failure modes of the two loess at different water content are producing large plastic deformation, and their shear strength declines with the increment of water content. Excavating the new tunnel causes extra deformation and stress to the existing tunnel lining. The higher the water content of loess, the greater the extra deformation and stress. When CFST piles are used to reinforce the stratum, the existing tunnel lining’s deformation and stress are significantly reduced. Considering the economy and the reinforcement effect, when the water content of loess is 8%, 14%, and 20%, respectively, the spacing of CFST piles is 1.6 m, 1.2 m, and 1.2 m, and the length is 25 m, 25 m, and 30 m, respectively.