下穿既有电缆隧道的地铁暗挖隧道稳定性研究

以北京地铁10号线二期终-火区间地铁暗挖隧道下穿2条电缆隧道工程为背景，通过地铁暗挖隧道施工的全程动态数值模拟，并基于现场初期支护收敛监测结果进行对比分析，研究砂卵石地层条件下地铁暗挖隧道初期支护收敛变形特点。结果表明： 1）地表最大沉降为6.46 mm，地铁隧道数值模拟得到的最大收敛值为7.10 mm，实测最大收敛值为6.77 mm，地铁隧道初期支护变形控制在合理、安全的范围内； 2）减小钢拱架间距和全断面注浆这2种技术措施对于提高地铁隧道初期支护及围岩的稳定性效果显著； 3）先施工的右线隧道对周边环境引起的损伤大，后施工的左线隧道对周边环境引起的损伤小； 4）先施工的隧道应设计更高的初期支护强度、全断面注浆等技术措施来保证隧道衬砌及围岩的稳定。

Study on Stability of Mined Metro Tunnel Crossing Underneath Existing Cable Tunnels

The mined tunnel of Ending-Huoqiying section of line 10 of Beijing Metro crosses underneath 2 existing cable tunnels.The features of the convergence of the primary support of the mined Metro tunnel located in sand-cobble ground are studied by means of dynamic simulation of the construction of the mined tunnel and comparison between the measured convergence and the simulation results.The study results show that：1）The maximum ground surface settlement is 6.46 mm,the maximum convergence of the primary support of the Metro tunnel obtained by numerical simulation is 7.10 mm,and the maximum convergence measured is 6.77 mm.The deformation of the primary support of the Metro tunnel is controlled within a safe and rational range; 2） The technical countermeasures adopted,i.e.,reducing the spacing of the steel ribs and performing full-face grouting,have good effect in improving the stability of the primary support and surrounding rock of the Metro tunnel ; 3） The right tunnel tube that is excavated first causes serious damage to the surrounding environment,while the left tunnel tube that is excavated later causes less damage to the surrounding environment; 4）Technical countermeasures,such as primary support with higher strength and full-face grouting,should be designed for the tunnel tube that is excavated first.