Objective In close-proximity projects such as newly built metro stations closely under-passing existing lines, the existing metro stations may experience significant settlement under construction disturbance, thereby affecting structural and line operational safety. Therefore, it is necessary to investigate the influencing law of construction disturbance from newly built metro stations on existing metro station structures.

Method Taking a project in China where a newly built metro station closely under-passes an existing metro station by mining method at zero distance as the engineering background, the project overview, design scheme of the new station mined section, as well as key construction technologies and construction sequences are briefly introduced. A three-dimensional model of the new station is established using finite element software and the construction process is simulated. The results are verified by comparison with field monitoring data. Based on numerical calculation results, the final settlement of the existing station and the deformation characteristics at key points are analyzed, and the influence of pilot tunnel excavation sequences on the structural deformation of existing station is further investigated.

Result & Conclusion  The monitoring results are generally in accordance with the simulated ones, thus verifying the accuracy and reliability of the numerical simulation method. By adopting composite construction techniques such as the CRD (cross diaphragm) method, multiple pre-support system, and grouting reinforcement, the technical challenge of settlement control is effectively solved through utilizing the rational transformation of the load-bearing system. Impacts of the new mined station construction on the existing station structural deformation are mainly characterized by the vertical displacement, with relatively minor influence on the horizontal displacement. In the spatial dimension, the settlement influence range of the new mined station on the existing station is approximately twice the width of the mined station, with the most unfavorable critical point located along the central axis of the existing station. In the temporal dimension, the excavation of pilot tunnels 6, 10, and 14 results in relatively large incremental settlement at key points of the existing station, which contributes 36.3%, 30.3%, and 20.5% to the final settlement respectively.