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| Mechanical behavior analysis of the construction process of a multi-arch tunnel without middle drift |
| TONG Yue1,2, ZHU Ziyue3, CHEN Junwu1, ZHANG Dongming3*, ZHANG Wei1
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1. Broadvision Engineering Consultants, Kunming 650041, Yunnan, China;
2. Investment Co., Ltd., of Yunan Communications Investment &
Construction Group Co., Ltd., Kunming 650228, Yunnan, China;
3. Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China |
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Abstract Multi-arch tunnels without middle drift were widely applied in regions with complex terrain and unfavorable geological conditions. However, the mechanisms of structural stress imbalance and mutual disturbance between the two caves during construction remained insufficiently understood. Based on Xiazhai Tunnel Project of Xuanhui Expressway in Yunnan, numerical simulations validated by field monitoring data were employed to analyze the mechanical response throughout the construction process of a multi-arch tunnel without a middle drift under different burial depths and bias pressures. The results indicated that the right shoulder, middle wall and right arch foot of the first tunnel were identified as dangerous areas, and the displacement of the first tunnel was significantly impacted by the construction of the following tunnel. When the bias angle was 25°, the vertical displacement of the right shoulder of the first tunnel caused by the upper step excavation of the following tunnel reached 25.9%. The horizontal convergence of the lower step line of the first tunnel was found to be significantly higher than that of the upper step line, and the middle wall and the right arch foot were identified as key stress concentration areas. Increasing burial depth was shown to enhance the self-weight stress of surrounding rock and thus increase the absolute deformation of the structure, while the strengthened confinement reduced the relative contribution of disturbance induced by following-tunnel excavation. Under increasing bias angle, the displacement on both sides of the bench line exhibited a left-leaning tendency, and the structural load-transfer path was altered. The initial support and secondary lining were most unfavorable under the 13° and 25° bias conditions respectively. The results demonstrated that when the buried depth exceeded 40 m or the bias was greater than 13°, the support of the middle wall and arch foot should be strengthened. This research provided a quantitative basis and engineering reference for stability control of multi-arch tunnels without a middle drift under complex geological conditions.
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Published: 23 March 2026
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