大直径地铁盾构隧道下穿高铁明挖隧道方案研究

天津某地铁盾构区间超深埋隧道下穿京津城际线解放路明挖隧道,工程处于软土地层,地质条件差,工程风险大。为探究盾构下穿对高铁明挖隧道的影响,首先对高铁明挖隧道现状进行调查,对外径6.6 m双线盾构依次下穿高铁明挖隧道4种方案的优缺点进行比选分析,并运用有限元数值模拟手段对优选方案进行分析计算。结果表明:(1)高铁明挖隧道现状良好,最大不均匀沉降为0.7 mm;(2)盾构下穿绕避高铁明挖隧道地连墙方案可行性及安全性均优于其他方案,该方案对高铁既有结构不会造成直接破坏,模拟计算结果能够满足相关规范要求(沉降<2 mm),方案安全可行。

Study on the Large Diameter Subway Shield Tunnel Undercrossing Open-Cut Tunnel of High Speed Railway

An ultra-deep buried tunnel of a subway shield section of Tianjin passes through the open-cut tunnel of Jiefang Road on the Beijing-Tianjin Intercity Railway.The project is located in a soft soil layer with poor geological conditions and high engineering risks.Since the high speed railway tunnel has strict requirements on structural deformation control,in order to reduce the influence of shield tunneling on the high speed railway tunnel,investigation was carried out on the current situation of the high speed railway tunnel before the construction of the shield tunnel.Pros and cons of four schemes of the shield tunnel with outer diameter of 6.6m were discussed.Optimal scheme was calculated by the finite element numerical simulation before starting the construction.The results show:(1)The present condition of the high-speed railway open cut tunnel is good with uneven settlement which is small.(2)The scheme avoiding undercrossing the continuous concrete wall of high-speed railway open cut tunnel is suggested rather than the other projects.The scheme has no direct damage to existing structures and meet the requirements of specifications for deformation control(≤2 mm).