盾构近距下穿既有地铁盾构隧道施工参数控制

为研究盾构下穿既有盾构隧道时施工参数的合理取值，以北京南水北调东干渠工程盾构隧道穿越既有地铁盾构隧道施工为依托，通过对既有隧道沉降的数值模拟和现场监测数据、盾构施工参数的分析，讨论了既有左右线隧道沉降存在差异的原因，总结了控制沉降的施工参数经验，阐述了既有隧道受穿越施工扰动的沉降规律，提出并验证了盾构隧道病害整治的方法.研究结果表明:受盾构施工参数的影响，既有左线隧道沉降23.9 mm，而右线仅沉降4.8 mm，沉降差异明显，但规律基本一致；盾构施工时，土仓压力调整级差不宜大于0.005 MPa，严格控制同步注浆压力在0.50 MPa，二次补浆压力在0.20~0.35 MPa，曲线段适当减缓掘进速度；已投入运营的地铁维修作业时间短，宜通过化学注浆治理管片接缝和螺栓孔处的渗漏水，压力注胶充填树脂治理道床裂缝. 

Construction Parameters Control of Shield Tunnel Underneath Traversing Existing Dual Shield Tunnels

In order to investigate reasonable construction parameters of a shield tunnel underneath traversing existing dual shield tunnels, the project that shield tunnel of the East Trunk Canal of the South-to-North Water Diversion Project traversed subway shield tunnels in Beijing was studied as an example. The reason for the difference in settlement between the left and right tunnels was determined by analyzing the numerical simulation and in situ monitoring data of the settlement of existing tunnels and the shield construction parameters. Then, the construction parameters for controlling settlement were given. Moreover, the trends in the variation in settlement of existing tunnels caused by traversing construction was discussed and some measures to counter shield tunnel diseases were proposed and verified. The results show that because of the influences of shield construction with different parameters, the final settlement of the existing left tunnel is 23.9 mm, while that of the right tunnel is only 4.8 mm. Although the settlements of the two tunnels differ significantly, their trends in variation are almost consistent. During the construction, the adjusted range of the working chamber pressure should not be more than 0.005 MPa and the synchronous grouting pressure should be adjusted accurately to be 0.50 MPa. Meanwhile, the secondary grouting pressure should be 0.20-0.35 MPa, and the tunneling speed in the curve section is required to slow down appropriately. Since the maintenance time in a subway is short, chemical grouting is adopted to solve the problem of leakage of water in segment joints and bolt holes while a pressure filling resin is used to repair the cracks in the slab.