Calculation Method of Surrounding Rock Pressure for Shallow and Unsymmetrical Tunnel under Deep Valley Terrain

Bai, Zhe; Wu, She–Ching

doi:10.4028/www.scientific.net/amm.170-173.1382

Cited by 3 publications

(1 citation statement)

References 5 publications

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“…The current researches on shallow and asymmetrically loaded tunnel mainly focus on the following aspects, namely the calculation of tunnel overlying surrounding rock pressure (Qiu et 2015) constructed the failure model of tunnel with shallow buried and asymmetrical loading, and deduced the upper bound solution of the tunnel overlying surrounding rock pressure based on the principle of virtual power. Zuo (2011) and Bai et al (2012) pointed out that the overlying surrounding rock pressure calculation of shallow and asymmetrically loaded tunnel recommended in 'Code for design of road tunnel in China' (JTG 3370.1-2018) had limitations. Therefore, the calculation formula was modi ed by constructing a new calculation model or programming method, and the modi ed formula was veri ed with the simulated results and measured data in actual engineering.…”

Section: Introductionmentioning

confidence: 99%

Failure mechanism and treatment measures of supporting structures at the portal for a shallow buried and asymmetrically loaded tunnel with small clear-distance

et al. 2022

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The construction of tunnel portal not only has to face the challenges of complex geological conditions such as shallow buried and asymmetrically loaded, but also needs to consider the adverse effects of factors such as the layout form of the tunnel. Thus, the construction of portal has always been the di culty and focus of tunnel engineering construction. Under the coupling of multiple adverse factors such as complex geological conditions and special layout form, the tunnel portal is prone to excessive deformation, supporting structures cracking and even collapse during the excavation. In this study, a shallow buried and asymmetrically loaded tunnel with small clear-distance in northwest China was taken as an engineering case. Aiming at the distresses of slope instability, peeling off and block falling of primary support concrete and cracking of secondary lining concrete in the tunnel portal construction, combined with eld investigation, statistical analysis, numerical simulation and deformation monitoring, the failure mechanism of supporting structures was deeply studied, and the corresponding treatment measures were proposed. The research results indicated that the loose and broken gravel soil in the shallow buried section, asymmetrical loading, surface water in ltration, and short construction spacing between two tunnels were the main triggers of supporting structures failure. Affected by the topographic bias, the loose load generated by the surrounding rock on the deep buried side squeezed the entire tunnel to the shallow buried side after the portal excavation. And this deformation trend became more signi cant after the gravel soil was deteriorated by water immersion. The retaining wall produced a clockwise rotation deformation around the wall corner in the process of limiting the tunnel deviation, and the local wall body cracked due to the excessive tensile stress. The primary support concrete and secondary lining concrete produced excessive asymmetrical deformation because of the signi cant asymmetrical loading. The concrete with excessive deformation was cracked by obvious tensile or shear stress. The following tunnel excavation had a signi cant negative impact on the stability of the prior tunnel. Combining the failure mechanism of the supporting structures and the characteristics of the continuous development of cracks, the treatment measures of 'stabilize the stratum rst and then treat the cracks' were proposed, including the back lling and tamping the shallow buried side at tunnel portal, reinforcing the interlaid rock by ground surface grouting, setting intercepting ditch at the slope top, staggering a certain safe excavation distance between the following tunnel and the prior tunnel. The eld monitoring and patrol inspection results indicated that the proposed treatment measures had achieved the expected results. The research results can provide corresponding construction experience and suggestions for similar projects in the future.

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Section: Introductionmentioning

confidence: 99%

Failure mechanism and treatment measures of supporting structures at the portal for a shallow buried and asymmetrically loaded tunnel with small clear-distance

et al. 2022

View full text Add to dashboard Cite

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Study on the Applicability of Load Calculation Method for Large-Diameter Shield Tunnel in Argillaceous Sandstone Stratum under High Water Pressure

Tan,

Wang

2023

KSCE J Civ Eng

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Failure mechanism and treatment measures of supporting structures at portal for a shallow buried and asymmetrically loaded tunnel with small clear-distance

Chen

Lai

Huang

et al. 2022

Preprint

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The construction of tunnel portal not only has to face the challenges of complex geological conditions such as shallow buried and asymmetrically loaded, but also needs to consider the adverse effects of factors such as the layout form of the tunnel. Thus, the construction of portal has always been the difficulty and focus of tunnel engineering construction. Under the coupling of multiple adverse factors such as complex geological conditions and special layout form, the tunnel portal is prone to excessive deformation, supporting structures cracking and even collapse during the excavation. In this study, a shallow buried and asymmetrically loaded tunnel with small clear-distance in northwest China was taken as an engineering case. Aiming at the distresses of slope instability, peeling off and block falling of primary support concrete and cracking of secondary lining concrete in the tunnel portal construction, combined with field investigation, statistical analysis, numerical simulation and deformation monitoring, the failure mechanism of supporting structures was deeply studied, and the corresponding treatment measures were proposed. The research results indicated that the loose and broken gravel soil in the shallow buried section, asymmetrical loading, surface water infiltration, and short construction spacing between two tunnels were the main triggers of supporting structures failure. Affected by the topographic bias, the loose load generated by the surrounding rock on the deep buried side squeezed the entire tunnel to the shallow buried side after the portal excavation. And this deformation trend became more significant after the gravel soil was deteriorated by water immersion. The retaining wall produced a clockwise rotation deformation around the wall corner in the process of limiting the tunnel deviation, and the local wall body cracked due to the excessive tensile stress. The primary support concrete and secondary lining concrete produced excessive asymmetrical deformation because of the significant asymmetrical loading. The concrete with excessive deformation was cracked by obvious tensile or shear stress. The following tunnel excavation had a significant negative impact on the stability of the prior tunnel. Combining the failure mechanism of the supporting structures and the characteristics of the continuous development of cracks, the treatment measures of ‘stabilize the stratum first and then treat the cracks’ were proposed, including the backfilling and tamping the shallow buried side at tunnel portal, reinforcing the interlaid rock by ground surface grouting, setting intercepting ditch at the slope top, staggering a certain safe excavation distance between the following tunnel and the prior tunnel. The field monitoring and patrol inspection results indicated that the proposed treatment measures had achieved the expected results. The research results can provide corresponding construction experience and suggestions for similar projects in the future.

show abstract

Calculation Method of Surrounding Rock Pressure for Shallow and Unsymmetrical Tunnel under Deep Valley Terrain

Cited by 3 publications

References 5 publications

Failure mechanism and treatment measures of supporting structures at the portal for a shallow buried and asymmetrically loaded tunnel with small clear-distance

Failure mechanism and treatment measures of supporting structures at the portal for a shallow buried and asymmetrically loaded tunnel with small clear-distance

Study on the Applicability of Load Calculation Method for Large-Diameter Shield Tunnel in Argillaceous Sandstone Stratum under High Water Pressure

Failure mechanism and treatment measures of supporting structures at portal for a shallow buried and asymmetrically loaded tunnel with small clear-distance

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