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Study on the Failure Modes of a New Tunnel Adjacent to an Existing Building
(Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031)
Abstract The primary impact of construction of a new tunnel adjacent to an existing building is the redistribution of surrounding rock stress, which results in variations to a series of mechanical behaviors. This paper introduces the strength reduction method and the numerical simulation for studying the failure modes during the construction of a new tunnel approaching existing buildings. The results indicate that when the new tunnel is far from the existing buildings, the instability affects only the tunnel itself, not the buildings; however, when the new tunnel is adjacent to the buildings, the rock sandwiched between them is damaged. Based on the different failure modes, the following criteria are presented for judging whether or not the new tunnel construction influences the existing buildings: 1) If the tunnel depth is fixed (namely at a direction of 0°), and when the safety factor obtained by the strength reduction method is tending to be constant, then it can be used as a criterion regarding the inluence. If the tunnel depth is varied (namely not at a direction of 0°), the safety factor can be used as a criterion only when it reaches the peak; 2) Whether or not the slip band indicated by the shear strain increment goes through the sandwiched rock between the tunnel and buildings, it can be regard as the intuitive criterion regarding the influence. The research findings provide a theoretical foundation for managing the safety risk, studying the influence zoning and establishing corresponding standards and specifications in the future.
Abstract：
The primary impact of construction of a new tunnel adjacent to an existing building is the redistribution of surrounding rock stress, which results in variations to a series of mechanical behaviors. This paper introduces the strength reduction method and the numerical simulation for studying the failure modes during the construction of a new tunnel approaching existing buildings. The results indicate that when the new tunnel is far from the existing buildings, the instability affects only the tunnel itself, not the buildings; however, when the new tunnel is adjacent to the buildings, the rock sandwiched between them is damaged. Based on the different failure modes, the following criteria are presented for judging whether or not the new tunnel construction influences the existing buildings: 1) If the tunnel depth is fixed (namely at a direction of 0°), and when the safety factor obtained by the strength reduction method is tending to be constant, then it can be used as a criterion regarding the inluence. If the tunnel depth is varied (namely not at a direction of 0°), the safety factor can be used as a criterion only when it reaches the peak; 2) Whether or not the slip band indicated by the shear strain increment goes through the sandwiched rock between the tunnel and buildings, it can be regard as the intuitive criterion regarding the influence. The research findings provide a theoretical foundation for managing the safety risk, studying the influence zoning and establishing corresponding standards and specifications in the future.
ZHANG Hui-Jian- Chou-Wen-Ge- Kong- Chao
.Study on the Failure Modes of a New Tunnel Adjacent to an Existing Building[J] MODERN TUNNELLING TECHNOLOGY, 2016,V53(4): 97-101
2016, Vol. 53 