Retracted: Study on Construction Time of Secondary Lining for Large Section Shallow Buried Tunnel in Soft Rock

Zhang, Jianguo; Wang, Xiaoyun; Wang, Shan; Wen, Shulian

doi:10.1109/icscse.2016.0084

Cited by 2 publications

(2 citation statements)

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“…The "space-time effect" of the excavation face can be divided into two stages: the "spatial effect" and "time effect" [21,22] (as shown in Figure 11); the "spatial effect" mainly acts on the S 1 section, whereas the "time effect" corresponds to the rheology of the surrounding rock, which is mainly reflected in the S 3 section. However, the initial support of the tunnel is generally completed in the BC section and the CD section is mainly the equilibrium and stable stage of the interaction between the surrounding rock and the supporting structure.…”

Section: Theoretical Analysismentioning

confidence: 99%

Research on the Prediction of the Time of Initial Support of Soft Rock Tunnel Based on the Optimized Longitudinal Deformation Profile

et al. 2022

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The longitudinal deformation profile (LDP) of the surrounding rock can intuitively and effectively reflect that the deformation of the surrounding rock of the tunnel wall is affected by the “spatial effect” at the front end of the excavation face during the tunnel excavation process, and provides a theoretical basis for the best time for the construction of the supporting structure. Taking a large-section tunnel of soft rock as an example, the LDP equation (displacement release coefficient) of the surrounding rock is derived based on Unlu and Gercek, and the optimization and improvement are proposed after comprehensively considering Poisson’s ratio, the elastic modulus, cohesion, internal friction angle, blasting parameters, etc., using FLAC3D to analyze the rationality and validity of improving the LDP equation of the surrounding rock. The results show that: (1) by adding the “expanded convergent function” in the x ≥ 0 section, the LDP equation of surrounding rock is optimized and improved, and the correlation coefficient of the data is increased from the original R-square = 0.8 to R-square = 0.95; (2) by comparing with the numerical simulation data, the improved LDP equation of the surrounding rock can better match it, which confirms that the improved LDP equation of surrounding rock is more reasonable and practical; (3) it is proposed that the displacement release coefficient value is the best time to apply support when the displacement increment of the surrounding rock has a sharp increase point, and it is concluded that when the Class-III surrounding rock is constructed by the long step method, it is best to start supporting at about x = 2.24 m from the tunnel face. When the Class-IV surrounding rock is constructed by the reserved core soil method, it is best to start supporting at about x = 1.47 m from the face of the tunnel.

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Section: Theoretical Analysismentioning

confidence: 99%

Research on the Prediction of the Time of Initial Support of Soft Rock Tunnel Based on the Optimized Longitudinal Deformation Profile

et al. 2022

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“…Feng et al [29] found that the reasonable secondary lining supporting time of soft rock tunnels is 24~25 days after excavation. Zhang et al [30] analyzed a substantial amount of shallow buried tunnel displacement monitoring data in soft rock. Construction of the secondary lining is permissible when the tunnel vault's settlement rate is below 0.49 mm/d and the side wall's horizontal absolute convergence rate is below 0.15 mm/d.…”

Section: Introductionmentioning

confidence: 99%

Study on Large Deformation Characteristics and Secondary Lining Supporting Time of Tunnels in Carbonaceous Schist Stratum under High Geo-Stress

Tan,

Chen,

Liu

2023

Sustainability

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The deformation characteristics and the timing for secondary lining support in high geo-stress soft rock tunnels have drawn significant attention. In carbonaceous shale formations, tunnel construction deformations are very pronounced under construction disturbances due to the development of joints, dense fractures, and poor interlayer bonding. With the Xishuangbanna tunnel as our research backdrop, this study meticulously analyzed the deformation patterns and characteristics inherent to high geo-stress tunnels constructed within carbonaceous schist formations. Employing a comprehensive approach involving full displacement analysis and on-site construction mechanics testing, we utilized the displacement release rate and structural safety factors as key indicators to determine the secondary lining supporting time. Employing this innovative approach, we successfully identified the ideal junctures for implementing secondary lining support in tunnels excavated through high geo-stress carbonaceous schist. The research findings indicate that the primary damage modes in high geo-stress carbonaceous schist tunnels are initial support failure and extensive early support deformation. These vulnerabilities are primarily attributed to weak and fragmented strata, elevated ground stress levels, and inadequate support strength. During the early stages of tunnel construction, substantial deformations are observed, exhibiting high rates of change. Horizontal convergence, notably, significantly surpasses the settlement at the tunnel’s crown. When employing the three-bench method for construction, the deformation occurring before the excavation of the middle bench contributes the most to the total deformation monitored, whereas the deformation generated after the excavation of the inverted arch constitutes a minor proportion. The tunnel’s crown and invert experience tension while the secondary lining undergoes compression. The internal forces are most significant at the tunnel’s hance and knee, with the left tunnel knee being the weakest section of the secondary lining. The findings of our study are poised to guide the design and execution of tunnels constructed within high geo-stress carbonaceous schist formations.

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Retracted: Study on Construction Time of Secondary Lining for Large Section Shallow Buried Tunnel in Soft Rock

Cited by 2 publications

References 0 publications

Research on the Prediction of the Time of Initial Support of Soft Rock Tunnel Based on the Optimized Longitudinal Deformation Profile

Research on the Prediction of the Time of Initial Support of Soft Rock Tunnel Based on the Optimized Longitudinal Deformation Profile

Study on Large Deformation Characteristics and Secondary Lining Supporting Time of Tunnels in Carbonaceous Schist Stratum under High Geo-Stress

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