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| Research on stability of excavation face of shield tunnel undercrossing station in water-rich gravel stratum |
| XIAO Pengfei1, FENG Guangfu1, JIA Shaodong1, MENG Qingjun1, WANG Shuying2, LIU Aolin2
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1. Nanning Rail Transit Co., Ltd., Nanning 530000, Guangxi, China;
2. School of Civil Engineering, Central South University, Changsha 410075, Hunan, China |
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Abstract Based on the project of Nanning Metro Line 5 undercrossing Guangxi University Station of Line 1 in Xinguang Section, FLAC3D software was used to study the stability of the excavation face of the shield tunnel undercrossing the water-rich gravel stratum of the station bottom plate at ultra-close distance. The influence of support stress ratio and groundwater level on the stability of excavation face was explored, and the appropriate supporting pressure control value of excavation face was given as the technical guidance for field construction. The research showed that with the decrease of the support stress ratio, the horizontal displacement of the soil on the excavation face increased continuously, and its deformation conformed to the development trend of the soil plastic zone. The failure mode of the excavation face in the water-rich gravel stratum was wedge-shaped ahead of the excavation, and the failure area gradually developed to the bottom plate of the existing station structure. After the instability and failure of the excavation face, the bottom plate of the station structure and the soil belowed the bottom plate form the free surface; with the increase of groundwater level, the supporting stress ratio of instability failure of excavation face increased, and the stability of excavation face decreased significantly. The earth pressure should be controlled above 111 kPa when crossing station.
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Received: 31 December 2020
Published: 20 March 2021
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