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| Effects of twin tunneling underneath on existing shield tunnels |
| GAN Xiaolu1，2，3，YU Jianlin1，2，3，GONG Xiaonan1，2，3，ZHU Min4，CHENG Kang1，2，3，5 |
| (1. Research Center of Coastal and Urban Geotechnical Engineering，Zhejiang University，Hangzhou，Zhejiang 310058，China；2. Key Laboratory of Soft Soils and Geoenvironmental Engineering of Ministry of Education，Zhejiang University，Hangzhou，Zhejiang 310058，China；3. Engineering Research Center of Urban Underground Development，Zhejiang University，Hangzhou，Zhejiang 310058，China；4. College of Civil and Transportation Engineering，Shenzhen University，Shenzhen，Guangdong 518060，China；5. China Railway 11th Bureau Group Co. Ltd.，Wuhan，Hubei 430061，China) |
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Abstract The twin tunneling may induce settlements of the overlying tunnels and lead to adverse influences on the operation of the existing tunnels. The Pasternak elastic foundation beam theory and Loganathan-Polous solution are used to propose a simplified analysis method for evaluating the responses of existing tunnels to new twin tunneling underneath. The relationship between the ground losses induced by the first and second tunnel excavation is described by an exponential equation. The effectiveness of the proposed method is verified by measurement data from a case study. Based on the verified method，a parametric analysis is performed to investigate the influences of the horizontal distance between the twin tunnels，the ground loss and the pillar depth on the tunnel responses. The results show that the proposed method considering the ground loss differences between twin tunnels can derive more accurate calculation results. Increasing the horizontal distances between the twin tunnels and the pillar depth and reducing the ground loss are able to alleviate the tunnel settlements caused by twin tunneling underneath. These parameters have apparent effects on the settlements and bending moments of existing tunnels. The proposed method can provide a theoretical basis for predicting the influences of new twin tunnels excavation on the existing tunnel in relevant engineering practice.
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2020, Vol. 39 
