Abstract
The methodology of the existing displacement control is illustrated taking the shield of twin tunnels of Line 4 underpassing the upline tunnel of existing metro Line 1, for example. Vertical, horizontal, and convergence displacement of the existing tunnel is monitored and analyzed in detail in this paper. Shield parameters are predefined and adjusted based on the feedback of the displacement of Line 1. Short-term displacement of the existing tunnel is greatly influenced by the relative distance between the shield face and the existing tunnel and shield parameters. The shapes of horizontal and convergence displacement curves are similar. Line 1 is reinforced, and a new analysis method is firstly proposed for the design of reinforcement of the existing tunnel which is verified by the analytical methods derived from prior studies. The results show that the change of reinforcement stiffness has a greater effect on the normalized bending moment and the normalized shear force of the existing tunnel, and reinforcement of 25 rings on either side of the intersection point is the best choice in this case. The proposed model can be widely applicable for reinforcement design and safety check of the existing tunnel.
Highlights
The interaction between new shield construction and existing tunnel has become a common and important issue with the rapid development of underground traffic system, which has been studied in the past using a variety of approaches: field observations, model tests, analytical methods, and finite element modeling
Based on the abovementioned statements, the response of the existing tunnel is analyzed, and analytical methods are proposed for verification and the reinforcement design
Main conclusions derived from the analysis are as follows: (1) The displacement of the existing tunnel changes with the relative position of the shield and the existing tunnel
Summary
The interaction between new shield construction and existing tunnel has become a common and important issue with the rapid development of underground traffic system, which has been studied in the past using a variety of approaches: field observations, model tests, analytical methods, and finite element modeling. Kim and Liu et al [1, 2] presented a good summary comparison of the studies and only studies that illustrates the shield underpassing or parallel underpassing the existing tunnel. Yamaguchi et al [3] presented successively the numerical model and analyzed three configurations of the twin tunnels in Japan: aligned horizontally, vertically, and inclined. The construction of the upper tunnel at first leads to both higher settlement and bending moment. The maximum soil settlement was obtained for vertical-aligned tunnels, while horizontal-aligned tunnels caused the lowest settlement. Addenbrooke and Potts [4] analyzed the influence of tunnel position, tunnel spacing, rest period, and sequence of excavation on the interaction between the two tunnels
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