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| The effect of upper step length on tunnel deformation in tunnel step construction |
| LI Zhao1, LIANG Qingguo1,2*, SUN Wen1, CAO Xiaoping1,2
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1. School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou 730070, Gansu, China;
2. Key Laboratory of Road & Bridge and Underground Engineering of Gansu Province, Lanzhou 730070, Gansu, China
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Abstract In order to study the effect of upper step length on tunnel deformation in tunnel step construction, the stability of surrounding rock and supporting structure was analyzed by using three dimensional finite element model, taking the step length and circular excavation length of a tunnel in Gansu province as parameters. The results showed that the length of the upper step had a significant impact on the plastic area range, surrounding rock stress, arch subsidence and surrounding convergence; the maximum surface settlement gradually increases. Besides 25 m from the tunnel center line, the surface settlement growth rate slows down and stabilizes; the length of the upper step is 1~1.5 times, about 15 m, and the circulating excavation meter was 1.5 m. During the tunnel construction, the monitoring results of surrounding rock displacement and surface settlement met the construction safety requirements, and verify the safety and accuracy of the analysis of the model data analysis. The research results can provide some reference for the tunnel constructed by step method.
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Received: 08 October 2021
Published: 20 March 2022
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