Abstract: Taking interval tunnel from Dazhongsi station to Jimenqiao station of Beijing metro line 12 crossing underneath Jingzhang high-speed railway tunnel as the engineering background, the three-dimensional finite element numerical simulation of underground tunnel passing through Jingzhang tunnel was established, based on the protection design of high-speed railway tunnel. The variation characteristics of vertical displacement and transverse displacement of Jingzhang tunnel changing with construction steps were summarized. Through site monitoring, the results of the concealed excavation tunnel vault settlement and structural convergence were analyzed. Besides, the vertical displacement, lateral displacement, structural convergence and automatic monitoring results of Jingzhang tunnel were also analyzed in detail. The research results show that: firstly, the vertical displacement process of Jingzhang tunnel can be summarized as a two-stage “S” curve; secondly, the area within the front 16 m and the back 14 m of the center of Jingzhang tunnel is the area significantly affected by the crossing construction; thirdly, the vertical displacement of Jingzhang tunnel caused by the construction of the advanced and post tunnels accounts for 68.3% and 31.7% of the total vertical displacement respectively, and the construction of the advanced tunnel is the key stage of railway tunnel protection. Numerical calculation and field monitoring show that the spatial position change of the vertical displacement of the railway tunnel is obviously affected by the post construction tunnel. The transverse uneven settlement of Jingzhang tunnel is obvious, with the maximum value 1.267mm. Based on the field monitoring results, the relevant displacement of the underground tunnel and Jingzhang tunnel does not exceed 44% of the allowable value. It can be considered that the design parameters and construction protection scheme of the underground tunnel meet the protection requirements of railway tunnel.

Key words: tunnel engineering; concealed excavation; metro tunnel; Jingzhang railway tunnel; protective measures; numerical calculation; site monitoring

摘要： 以北京地铁12号线大钟寺站—蓟门桥站区间暗挖隧道下穿京张高速铁路隧道为工程背景，在高速铁路隧道保护设计的基础上，建立了暗挖隧道下穿京张隧道三维有限元数值模拟，总结了京张隧道竖向位移和横向位移随施工步变化特征。通过现场监测，对暗挖隧道拱顶沉降和结构收敛监测结果以及京张隧道竖向位移、横向位移、结构收敛及自动化监测等结果进行了详细分析。研究结果表明：京张隧道竖向位移变化过程为两阶段“S”型曲线；京张隧道中心前16 m和后14 m范围内是穿越施工显著影响区域；先行和后行隧道施工引起的京张隧道竖向位移分别占总竖向位移的68.3%和31.7%，先行隧道施工是铁路隧道保护关键阶段；数值计算和现场监测表明后施工隧道对铁路隧道竖向位移的空间位置变化作用明显；京张隧道横向不均匀沉降明显，最大值为1.267 mm；综合现场监测结果，暗挖隧道和京张隧道相关位移不超过容许值的44%，可认为暗挖隧道设计参数和施工保护方案符合铁路隧道保护要求。

关键词: 隧道工程；暗挖；地铁隧道；京张隧道；保护措施；数值计算；现场监测