为探究超大直径盾构隧道下穿既有地下结构群的相互作用机制，以成都市典型地层条件为背景，利用Plaxis-3D软件模拟新建双华路隧道下穿既有成都地铁10号线和成贵高铁隧道结构，揭示超大直径盾构隧道下穿既有地下结构群的变形影响机制及遮帘阻隔效应。研究结果表明： 1）在设计埋深为2.4D（D为洞径）及不采取任何加固措施时，既有地下结构群沉降均超过规范限值； 通过增加新建隧道埋深，既有地下结构群沉降减小，当埋深增加2D时，沉降减小至规范限值之内； 通过采用180°和360°注浆措施对新建隧道周围土体进行加固时，既有地下结构群沉降明显减小，180°注浆加固可将沉降控制在规范限值之内，360°注浆的沉降控制效果最好。2）成贵高铁隧道的直墙拱形断面在开挖过程中底板变形最为明显，底板左右两侧底脚处横向位移变形曲线几乎重合，竖向位移随着下穿进程呈现交错领先现象。3）既有成都地铁10号线的圆形断面椭圆率整体呈下降趋势，在与新建隧道接近时下降最为明显，在远离时逐渐趋于不变。4）通过比较既有地铁隧道仅存在单线时的断面椭圆率变化可以看出，既有地下结构群的断面椭圆率下降程度均有所减小，表明隧道群间的相互作用使得既有地下结构群受新建隧道下穿的影响有所下降，即存在遮帘阻隔效应。

Herein, the Plaxis-3D software is employed to simulate the Shuanghua road tunnel crossing beneath the existing Chengdu metro line 10 and the Chengdu-Guiyang high-speed railway tunnel structures within typical Chengdu strata, revealing the deformation impact mechanisms and curtain barrier effect of a large-diameter shield tunnel undercrossing existing underground structure clusters. The research findings are summarized as follows: (1) At a design burial depth of 2.4D (where [D denotes the tunnel diameter) and without any reinforcement measures, the settlements of the existing structure clusters exceed the code-specified limits. Increasing the burial depth of the newly built tunnel correspondingly reduces the settlements of the existing structures, bringing them to within the allowable limits when the burial depth is increased by 2D. The implementation of grouting measures (180° and 360° coverages) to reinforce the new large-diameter tunnel considerably decreases the settlements of the existing structure clusters. Compared to 180° grouting, 360° grouting provides the most pronounced settlement control effect. However, 180° grouting also effectively controls settlements within the allowable limits. (2) For the Chengdu-Guiyang high-speed railway tunnel with its straight wall-arch section, the most pronounced deformation during excavation occurs at the base slab. The lateral displacements at the bottom-left and bottom-right corners of the base slab are nearly coincident, whereas their vertical displacements alternate in precedence as the undercrossing progresses. (3) The ovality of the circular cross-section of the existing Chengdu metro line 10 tunnel shows an overall decreasing trend along the undercrossing. The decrease is most notable as the new tunnel approaches and gradually stabilizes as it moves away. (4) By comparing the ovality changes of the cross-section when only one metro tunnel exists, it can be observed that the degree of ovality decrease of the existing tunnel clusters reduces. This indicates that the interaction within the tunnel clusters diminishes the impact of the new tunnel′s undercrossing on the existing underground structure clusters, demonstrating the existence of a curtain barrier effect.