研究目的: 针对在城市敏感区近距离穿越城市主干道下既有大断面隧道工程中变形控制难的问题,本文以北京地铁19号线下穿城市主干道下既有1号线隧道为背景,具有近距离穿越、隧道二衬混凝土无配筋,建设年代久远,裂缝病害、地层上硬下软等不利因素,项目穿越采取了洞外小导洞注浆、洞内芳纶布与钢板加固相结合的措施进行控制,同时工程通过分析计算与试验段确定最佳的盾构参数进行穿越,施工前对各项穿越措施进行了数值分析,对穿越方案与参数的确定起到指导作用,施工后根据监测结果对比分析,并验证了控制措施的可行性与数值计算的准确性。
研究结论: (1)采用洞外小导洞开挖注浆加固措施能够减小沉降,满足变形控制要求;(2)洞内钢板+芳纶布的结构加固措施能够有效增加既有地铁隧道的刚度,减小结构应力;(3)土仓压力、同步注浆压力最优取值范围为0.08~0.10 MPa和0.20~0.24 MPa;(4)数值模拟与现场监测结果对比偏差率不大于15.0%,能够有效预测盾构施工对既有结构的变形影响;(5)本文研究可为类似穿越工程控制措施的设计施工提供技术支撑。

Research purposes: For the problem of difficult deformation control in the project of crossing the existing large section tunnel under the city trunk road in the sensitive urban area, this paper takes the Beijing Metro Line 19 tunnel under the existing Line 1 under the city trunk road as the background, with such unfavorable factors like close crossing, tunnel second lining concrete without reinforcement, long construction age, crack disease, and hard and soft stratum. The project crossing adopts the combination of small guide hole grouting outside the hole, and aramid cloth and steel plate reinforcement inside the tunnel. At the same time, the project determines the best shield parameters for crossing through analytical calculations and test sections, and numerical analysis of the crossing measures is carried out before construction, which plays a guiding role in determining the crossing scheme and parameters. After construction, the feasibility of the control measures and the accuracy of the numerical calculation are verified by comparing and analyzing the monitoring results.
Research conclusions: (1) The project adopts small guide hole excavation grouting reinforcement measures which can reduce the settlement, and meet the requirements of deformation control. (2) The structural reinforcement measures of steel plate+aramid cloth in the tunnel can effectively increase the stiffness of the existing subway tunnel and reduce the structural stress. (3) The optimal values of soil pressure and synchronous grouting pressure are 0.08~0.10 MPa and 0.20~0.24 MPa. (4) The deviation rate between numerical simulation and field monitoring results is not more than 15.0%, which can effectively predict the influence of shield construction on the deformation of existing structures. (5) The research results can provide technical support for the design and construction of control measures for similar crossing projects.