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Geomechanics and Engineering Volume 31, Number 3, November10 2022 , pages 237-248 DOI: https://doi.org/10.12989/gae.2022.31.3.237 |
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Three-dimensional numerical parametric study of shape effects on multiple tunnel interactions |
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Liang Chen, Weiwei Pei, Yihong Yang and Wanli Guo
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| Abstract | ||
| Nowadays, more and more subway tunnels were planed and constructed underneath the ground of urban cities to relieve the congested traffic. Potential damage may occur in existing tunnel if the new tunnel is constructed too close. So far, previous studies mainly focused on the tunnel-tunnel interactions with circular shape. The difference between circular and horseshoe shaped tunnel in terms of deformation mechanism is not fully investigated. In this study, three-dimensional numerical parametric studies were carried out to explore the effect of different tunnel shapes on the complicated tunnel-tunnel interaction problem. Parameters considered include volume loss, tunnel stiffness and relative density. It is found that the value of volume loss play the most important role in the multi-tunnel interactions. For a typical condition in this study, the maximum invert settlement and gradient along longitudinal direction of horseshoe shaped tunnel was 50% and 96% larger than those in circular case, respectively. This is because of the larger vertical soil displacement underneath existing tunnel. Due to the discontinuous hoop axial stress in horseshoe shaped tunnel, significant shear stress was mobilized around the axillary angles. This resulted in substantial bending moment at the bottom plate and side walls of horseshoe shaped tunnel. Consequently, vertical elongation and horizontal compression in circular existing tunnel were 45% and 33% smaller than those in horseshoe case (at monitored section X/D = 0), which in latter case was mainly attributed to the bending induced deflection. The radial deformation stiffness of circular tunnel is more sensitive to the Young's modulus compared with horseshoe shaped tunnel. This is because of that circular tunnel resisted the radial deformation mainly by its hoop axial stress while horseshoe shaped tunnel do so mainly by its flexural rigidity. In addition, the reduction of soil stiffness beneath the circular tunnel was larger than that in horseshoe shaped tunnel at each level of relative density, indicating that large portion of tunneling effect were undertaken by the ground itself in circular tunnel case. | ||
| Key Words | ||
| shape; three-dimensional numerical analysis; tunnel stiffness; volume loss | ||
| Address | ||
| Liang Chen: Guangzhou Metro Design&Research Institute Co.,Ltd., Guangzhou, Guangdong, P. R. China Weiwei Pei and Yihong Yang: Wenzhou Design Assembly Company Ltd, Wenzhou 325000, China Wanli Guo: Geotechnical Engineering Department, Nanjing Hydraulic Research Institute, Nanjing 210024, China | ||