盖梁临时支撑对地铁隧道变形受力影响分析

Analysis on Impact of Temporary Support of Bent Cap on Force Deformation of Metro Tunnels

摘要:

城市高架桥改建工程难度大、风险高，不可避免会上跨既有地铁隧道施工。其中混凝土盖梁湿接缝施工所需的临时支撑会对下行运营期地铁的受力变形产生不利影响，威胁地铁运营安全。依托某邻近运营地铁隧道的城市快速路高架桥改建工程，对盖梁临时支撑荷载作用下的地铁隧道受力变形规律进行理论和实测分析，结果表明：（1）数值模拟结果与实测数据基本吻合，均呈“鼓腹形”变化，最大误差仅为0.087 mm；（2）隧道管片的受力变形随盖梁临时支撑作用距离和隧道埋深增加逐步减小，荷载至两隧道中心线距离由0 m增加至23 m时，最大竖向位移由0.4 mm减小至0 mm，拱顶和拱腰处弯矩分别下降10 %和5.8 %，隧道埋深由1.0 D增加至3.5 D时，最大竖向位移减小91.4 %，环向附加最大弯矩由25.9?kN?m减小至1.5 kN?m；（3）合适的临时支撑架设位置对于保障隧道结构安全至关重要，应根据隧道埋深和建设场地条件综合确定；（4）隧道拱顶受力变形对临时支撑作用较为敏感，需加强对拱顶范围内管片的监测。研究结果可为上跨运营期地铁的高架盖梁临时支撑的设计、施工和隧道施工监测提供技术参考。

Abstract:

The reconstruction project of urban elevated bridges is highly challenging and risky, and it is inevitable that the construction will cross the existing metro tunnels. The temporary supports required for the wet joint construction of concrete bent caps will have an adverse effect on the force deformation of the metro during the downward operation period, which threatens the operational safety of the metro. Relying on an urban expressway elevated bridge reconstruction project near the metro tunnel under operation, the theoretical and measured analysis is conducted on the force deformation rules of metro tunnel under the temporary support load of bent cap. The conclusions are as follows (1) the numerical simulation results are basically consistent with the measured data, both exhibiting a "bulging abdomen type" variation pattern. The maximum error is only 0.087 mm. (2) The force deformation of tunnel segments gradually decreases with the increase of the temporary support distance of the bent cap and the burial depth of the tunnel. When the distance from the load to the central line of two tunnels increases from 0 m to 23 m, the maximum vertical displacement decreases from 0.4 mm to 0 mm, while the bending moments at the vault and arch haunch reduce by 10 % and 5.8%, respectively. The burial depth of the tunnel increases from 1.0 D to 3.5 D, the maximum vertical displacement decreases by 91.4%, and the circumferential additional maximum bending moment decreases from 25.9 kN·m to 1.5 kN·m. (3) The appropriate position of erecting the temporary supports is crucial for ensuring the safety of the tunnel structure, which should be determined comprehensively based on the tunnel burial depth and the conditions of the construction site. (4) The force deformation of the tunnel vault is particularly sensitive to the temporary supports, which is required to strengthen the monitor of segments within the vault range. The research result can provide the technical references for the design and construction of temporary supports of elevated bent cap of metro lines spanning the operational metro and the monitoring of tunnel construction.