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<p>The cross-sectional shape is important in deep tunnel design since the deformation and rockburst of the tunnel surrounding rock vary much in the circular or horseshoe tunnels, especially the time-delayed deformation and rockburst. This work experimentally and numerically investigated the effects of cross-sectional shapes on the characteristics and mechanism of time-delayed deformation and rockburst in deep tunnels. A series of physical model tests were first carried out based on the prefabricated specimens with three cross-sectional shapes (circular, horseshoe, and tunnel with inverted arch). By varying the height-span ratio to characterize different cross-sectional shapes of the tunnel, the corresponding numerical simulations were then conducted on an engineering scale, and the recommended value was given for the engineering design. Notably, a multi-monitoring system, consisting of a high-speed camera, visual imaging correlation-2D (VIC-2D) techniques, distributed fiber optic sensing (DFOS), and an acoustic emission (AE) system, was integrated to monitor the mechanical response and failure process behavior of the surrounding rock. It is found that the surrounding rock experiences four distinct periods (quiet, propagation, violent, and failure) during the time-delayed deformation and rockburst process for the three cross-sectional shapes. Moreover, the failure characteristics of deep tunnels with various cross-sectional shapes were different. For the circular tunnel, the most severe locations of bursts were the crown and invert, while it was located at the arch footing and side walls for the horseshoe tunnel. Under the same loading path, the intensity of deformation and burst potential for a horseshoe tunnel was much greater than that of the other two cross-sectional shapes. During the engineering design stage, through comparative analysis of plastic zone development (<i>PZD</i>) and local energy release rate (<i>LERR</i>) as key indicators, the circular tunnel is considered to be the preferred cross-sectional shape, and the recommended height-span ratio ranges from 0.85 to 0.9 for the drilling and blasting tunnel. The research results guide the design of cross-section shapes in deep tunnels.</p>

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Physical Model Test and Numerical Modeling of Cross-Sectional Shape Effect on Evolution Mechanism of Time-Delayed Deformation and Rockburst in Deep Tunnels

  • 期刊论文

  • 发表日期：

    2025年9月9日

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  • Qiang Yang,
  • Zaobao Liu,
  • Xiaokai Wang,
  • Binhui Liu,
  • Feng Tian,
  • Xin Wang

摘要

The cross-sectional shape is important in deep tunnel design since the deformation and rockburst of the tunnel surrounding rock vary much in the circular or horseshoe tunnels, especially the time-delayed deformation and rockburst. This work experimentally and numerically investigated the effects of cross-sectional shapes on the characteristics and mechanism of time-delayed deformation and rockburst in deep tunnels. A series of physical model tests were first carried out based on the prefabricated specimens with three cross-sectional shapes (circular, horseshoe, and tunnel with inverted arch). By varying the height-span ratio to characterize different cross-sectional shapes of the tunnel, the corresponding numerical simulations were then conducted on an engineering scale, and the recommended value was given for the engineering design. Notably, a multi-monitoring system, consisting of a high-speed camera, visual imaging correlation-2D (VIC-2D) techniques, distributed fiber optic sensing (DFOS), and an acoustic emission (AE) system, was integrated to monitor the mechanical response and failure process behavior of the surrounding rock. It is found that the surrounding rock experiences four distinct periods (quiet, propagation, violent, and failure) during the time-delayed deformation and rockburst process for the three cross-sectional shapes. Moreover, the failure characteristics of deep tunnels with various cross-sectional shapes were different. For the circular tunnel, the most severe locations of bursts were the crown and invert, while it was located at the arch footing and side walls for the horseshoe tunnel. Under the same loading path, the intensity of deformation and burst potential for a horseshoe tunnel was much greater than that of the other two cross-sectional shapes. During the engineering design stage, through comparative analysis of plastic zone development (PZD) and local energy release rate (LERR) as key indicators, the circular tunnel is considered to be the preferred cross-sectional shape, and the recommended height-span ratio ranges from 0.85 to 0.9 for the drilling and blasting tunnel. The research results guide the design of cross-section shapes in deep tunnels.