近些年来，因曲线盾构施工造成的地面塌陷、桩基严重变形甚至开裂等不良影响时有发生，直接影响了上部结构的正常运行以及人民群众的财产安全。因此，研究曲线盾构侧穿既有桥梁对邻近桩基和地层的影响具有重要意义。本文以西安地铁16号线曲线盾构侧穿新西宝高速桥桩工程为背景，通过理论分析、数值模拟、室内试验、现场监测相结合的方法，展开曲线盾构侧穿对邻近桩基和地层的影响控制研究，主要工作内容和结论如下：

（1）通过研究盾构—地层—桩基之间的相互作用机理，发现曲线盾构隧道施工引起的地层扰动是造成地表沉降和桩基扰动的诱因。而地层自身的特性、盾构掘进参数的设置、曲线超挖的作用是影响曲线盾构对地层扰动的主要因素。为此控制曲线盾构施工对既有桩基影响的关键是控制这些主要因素对地层扰动的影响。

（2）应用ABAQUS软件建立曲线盾构侧穿既有桥桩有限元模型，分析了曲线盾构施工各阶段施工对上部地表以及邻近桩基的影响规律。研究表明，盾构主要沉降发生在盾构掘进阶段和盾尾脱离阶段，地表最大沉降位于曲线盾构内侧；桩基在盾构隧道范围内的水平位移变形最大；桩体最大竖向变形位于桩顶处，桩体竖向沉降量的大小和桩体与盾构隧道之间的水平净距有关，较小的水平间距会产生较大的竖向沉降。

（3）在曲线盾构侧穿施工过程中采取桩基注浆加固、渣土改良、曲线纠偏、掘进参数控制相结合的盾构施工控制技术优化措施。一方面通过增大桩基自身刚度的方法，减小桩基扰动变形。另一方面，通过减小盾构掘进过程中土体自身特性、曲线超挖以及掘进参数设置对地层扰动影响的方式，减小盾构施工对邻近桩基的扰动。

（4）通过对现场监测发现实际监测的地表沉降以及桥墩竖向沉降变形值均控制在规范控制允许值范围内，说明在现场采取的桩基注浆加固、渣土改良等盾构施工控制技术优化措施行之有效。

In recent years, adverse effects such as ground subsidence, serious deformation and cracking of pile foundations caused by curved shield tunnel construction have occurred from time to time, which directly affect the normal operation of the upper structure and the property safety of the people. Therefore, it is of great significance to study the control of the impact of curved shield tunnel construction on the neighboring pile foundation and soil layer during existing bridge crossing. Based on the background of Xi’an Metro Line 16 curved shield tunnel construction crossing Xixibao Expressway Bridge Pile Project, this paper carries out the research on the control of the impact of curved shield tunnel construction on adjacent pile foundation and soil layer by using a combination of theoretical analysis, numerical simulation, laboratory test and field monitoring. The main work contents and conclusions are as follows:

(1) By studying the interaction mechanism among shield, stratum and pile foundation, it can be found that the soil disturbance caused by curved shield tunnel construction is the cause of ground settlement and pile foundation disturbance. Moreover, the characteristics of the soil itself, the setting of shield driving parameters, and the impact of over-excavation in curves are the main factors affecting the soil disturbance by curved shield tunnel construction. Therefore, controlling the influence of these main factors on soil disturbance is the key to control the influence of curved shield tunnel construction on existing pile foundation.

(2) A finite element model of curved shield tunnel crossing existing bridge pile was established by using ABAQUS software, and the influence of curved shield tunnel construction at different stages on the ground surface and adjacent pile foundation was analyzed. The results show that the shield tunnel experiences the main settlement during the shield driving stage and the shield tail detachment stage, and the maximum ground settlement occurs at the inner side of the curved shield tunnel; the pile foundation within the range of shield tunnel undergoes the largest horizontal displacement and deformation; the pile top is the position of maximum vertical deformation of pile body; the vertical settlement of pile body depends on the horizontal clearance between pile body and shield tunnel, and a smaller horizontal clearance results in a larger vertical settlement.

(3) The optimization measures of shield construction control technology that combine grouting reinforcement, muck improvement, curve correction and driving parameter control were adopted in the process of curved shield tunnel crossing construction. On the one hand, the disturbance deformation of pile foundation was reduced by increasing the stiffness of pile foundation. On the other hand, the influence of soil characteristics, curve over-excavation and driving parameter setting on soil disturbance during shield driving was reduced to minimize the disturbance to the adjacent pile foundation caused by shield construction.

(4) Through on-site monitoring found, the surface settlement and vertical settlement deformation of bridge piers monitored in the field were all within the allowable range of the code control, indicating the effectiveness of the optimization measures of shield construction control technology adopted in the field, such as grouting reinforcement of pile foundation and muck improvement.

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