<p>Yielding layers have shown potential in controlling large deformations in tunnel support systems. However, the mechanical behavior and bearing capacity of shotcrete linings incorporating such yielding layers remain insufficiently quantified. This study investigates and compares the mechanical responses of shotcrete lining under rigid and yielding support through large-scale overloading model tests and numerical simulations. A key finding is that shotcrete linings with yielding layers exhibit a significantly prolonged elastic stage, indicating enhanced bearing capacity when the inner force and deformation evolution is categorized into elastic, plastic and unstable deformed stages. Taking the ultimate vertical geo-stress bore by shotcrete under rigid support as baseline, the overload safety factor of shotcrete lining with yielding layers is 1.67. Under rigid support, failure typically initiates at the haunch. In contrast, the presence of a yielding layer reduces ground pressure and shifts the failure zone to the inverted arch or arch springing. Furthermore, the influence of yielding layer thickness and rock strength on overload safety factor of shotcrete linings is discussed. According to the numerical results, the overload safety factor increases with the thickness of the yielding layer, but reduces with the weakening of surrounding rock strength. Increasing both the thickness and yielding strength of the layer can theoretically address support challenges in tunnels subjected to high geo-stress and weak surrounding rock. However, greater thickness will result in overbreak, while higher yielding strength demands proportionally stronger shotcrete. This study enhances understanding of the bearing capacity of shotcrete linings with yielding layers and provides guidance for support design in soft rock tunnel construction.</p>

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Model Test and Numerical Analysis of Bearing Characteristic of Shotcrete Lining with Yielding Layers

  • Bin-zhong Zhu,
  • Yu-chao Zheng,
  • Zhi-wen Yao,
  • Bao-lin Liao,
  • Wen-ge Qiu,
  • Hui-jian Zhang,
  • Kun Feng

摘要

Yielding layers have shown potential in controlling large deformations in tunnel support systems. However, the mechanical behavior and bearing capacity of shotcrete linings incorporating such yielding layers remain insufficiently quantified. This study investigates and compares the mechanical responses of shotcrete lining under rigid and yielding support through large-scale overloading model tests and numerical simulations. A key finding is that shotcrete linings with yielding layers exhibit a significantly prolonged elastic stage, indicating enhanced bearing capacity when the inner force and deformation evolution is categorized into elastic, plastic and unstable deformed stages. Taking the ultimate vertical geo-stress bore by shotcrete under rigid support as baseline, the overload safety factor of shotcrete lining with yielding layers is 1.67. Under rigid support, failure typically initiates at the haunch. In contrast, the presence of a yielding layer reduces ground pressure and shifts the failure zone to the inverted arch or arch springing. Furthermore, the influence of yielding layer thickness and rock strength on overload safety factor of shotcrete linings is discussed. According to the numerical results, the overload safety factor increases with the thickness of the yielding layer, but reduces with the weakening of surrounding rock strength. Increasing both the thickness and yielding strength of the layer can theoretically address support challenges in tunnels subjected to high geo-stress and weak surrounding rock. However, greater thickness will result in overbreak, while higher yielding strength demands proportionally stronger shotcrete. This study enhances understanding of the bearing capacity of shotcrete linings with yielding layers and provides guidance for support design in soft rock tunnel construction.