城市地铁隧道不可避免地将穿越大量的地下既有管线，施工扰动对隧道上覆管线产生附加内力和变形，将严重影响既有管线的安全使用。为保证在管线安全使用的前提下地铁隧道能够安全有序地进行施工，迫切需要研究地铁隧道施工对既有管线变形的影响规律和控制标准。论文以西安地铁工程为背景，构建地铁隧道施工影响下的地层沉降预测模型和考虑管-土分离影响下的管线受力变形分析模型，提出西安地铁隧道施工影响下上覆既有管线的变形控制标准。论文主要研究成果如下：

（1）基于随机介质理论建立了地铁隧道施工诱发的地层变形预测模型，并采用数值模拟方法分析了既有管线下地铁隧道开挖诱发的地层沉降规律。结果表明：隧道开挖影响下，既有管线对其上方地层沉降具有一定的抑制作用，尤其是管线刚度越大，其抑制作用越显著。因此，当管线刚度较大时，不能用地表沉降值代替管线沉降。

（2）将管线与土体相互作用下的变形划分为管-土紧密接触、管-土分离临界点和管-土分离三个阶段。建立了考虑管-土分离影响下的管线变形分析模型，研究了管线与隧道正交、斜交两种工况下的管-土分离范围。结果表明：西安地铁1号线某区间隧道施工诱发的管-土分离范围为16.272m（隧道中心线两侧各8.136m），最大管-土分离间隙4.2mm。

（3）基于建立的考虑管-土分离影响下的管线变形预测模型，分析了管-隧相对位置、管线埋深、材质、管径等主要因素对管线受力变形的影响规律。同时，对地铁隧道施工扰动下的上覆管线变形规律进行了数值分析研究。结果表明：地铁隧道施工影响下既有管线与地层之间存在管-土分离现象，且管-土分离范围约为隧道拱顶上方1.5倍隧道洞径。当管-隧相对位置、管线埋深、材质、管径等因素确定时，可将管线转角作为控制管线变形的关键性参数。

（4）将西安地铁1号线隧道沿线典型地质划分为三类，结合得到的考虑管-土分离影响下的管线受力变形模型，结合管线失稳验算，基于管线最大转角、地表最大允许沉降和地表最大允许倾斜率三个主要参数提出了西安地铁施工过程中不同管线埋深、材质及管径工况下的管线受力变形控制标准。

（5）基于本文提出的考虑管-土分离影响下既有管线受力变形分析模型及西安地铁施工影响下管线变形控制标准，采用理论计算和数值模拟相结合的方法完成了西安地铁1号线三类场地重要管线的安全性评估，针对存在安全隐患的管线提出具体的加固保护措施。现场监测结果表明本文制定的管线变形控制标准及加固措施合理有效，为防治地铁隧道施工诱发的上覆管线变形破坏问题提供了科学依据。

Urban metro tunnels will inevitably cross a large number of existing underground pipelines. Construction disturbance would produce additional internal force and deformation to the pipelines overlying the tunnel, which would seriously affect the safe use of existing pipelines. In order to ensure that the metro tunnel can be constructed safely and orderly on the premise of safe use of pipelines, it was urgent to study the influence law and control standard of metro tunnel construction on the deformation of existing pipelines. Base on the taking Xi'an metro project, this paper was constructed the prediction model of stratum settlement under the influence of metro tunnel construction and the prediction model of pipeline stress and deformation under the influence of pipe soil separation, and put forward the deformation control standard of existing pipeline under the influence of Xi'an metro tunnel construction. The main research results were as follows:

    (1) Based on the random medium theory, the prediction model of formation deformation induced by metro tunnel construction was established, and the numerical simulation method was used to analyze and explore the characteristics of formation settlement induced by metro tunnel under the existing pipeline. The analysis shows that under the influence of tunnel excavation, the existing pipeline has a certain inhibitory effect on the ground settlement above it, especially the greater the stiffness is, the more obvious the inhibitory effect is. Therefore, when the pipeline stiffness is large, the surface settlement value cannot be used to replace the pipeline settlement.

(2) The deformation under the interaction between pipeline and soil was divided into three stages: pipe-soil close contact, pipe-soil separation critical point and pipe-soil separation. The prediction model of pipeline deformation considering pipe-soil separation and a prediction model of pipe-soil separation range under orthogonal and oblique crossing conditions were established. It was obtained that the pipe-soil separation range induced by tunnel construction in a section of Xi'an metro line 1 was the pipeline within the horizontal distance of 16.272m (both sides of the tunnel center line are 8.136m), and the maximum pipe-soil separation gap was 4.2mm.

 (3) Based on the established prediction model of pipeline deformation considering the influence of pipe-soil separation, the influence laws of main factors such as relative position of pipe parts, pipeline material, pipe diameter and buried depth of pipeline on pipeline stress and deformation are analyzed. At the same time, the deformation law of overlying pipeline under the disturbance of subway tunnel construction was studied by numerical simulation method. The results shows that under the influence of subway tunnel construction, there is pipe-soil separation between the existing pipeline and the stratum, and the pipe-soil separation range is 1.5 times the tunnel diameter above the tunnel vault. When the relative position of pipe-tunnel, buried depth of pipeline, material, diameter and other factors are determined, the pipeline rotation angle can be used as the key parameter to control pipeline deformation.

   (4) The typical geology along the Xi'an metro line 1 tunnel was divided into three categories. Based on the obtained pipeline stress deformation model considering the influence of pipe-soil separation, combined with the pipeline instability checking calculation. Exploration of pipeline control standard are conducted from three main parameters of maximum pipeline angle, maximum allowable surface settlement and maximum allowable surface inclination rate. The control standard of different buried depth, material and pipe diameter in the construction of Xi'an metro were obtained.

   (5) Based on the existing pipeline deformation prediction model considering the influence of pipe-soil separation and the pipeline deformation control standard under the influence of Xi 'an metro construction. The safety assessment of important pipelines in three types of sites of Xi'an metro line 1 was completed by theoretical calculation and numerical simulation. Specific reinforcement and protection measures were proposed for pipelines with potential safety hazard. The field monitoring results show that the pipeline deformation control standards and reinforcement measures formulated in this paper are reasonable and effective, which provides a scientific basis for preventing and controlling the deformation and failure of the overlying pipelines induced by subway tunnel construction.