Abstract: With the continuous improvement of the urban rail transit network, it is inevitable that there will be adjacent or intersecting projects. The subway operation is very sensitive to the structural deformation, allowing for minimal deformation. To study the impact and response measures of deep excavation on the underlying regional transit tunnel, this article presents the municipal tunnel excavation project located directly above the Nanjing operating regional transit tunnel as a case history. The MIDAS-GTS geotechnical and tunnel simulation analysis software is used for numerical analysis. Based on the influence of spatial effects, the symmetrical zoning is adopted for deep excavation, and anti-buoyancy pipe curtains are established. The evaluation results are as follows: (1) During the deep excavation process, the vertical displacement generated by the underlying regional transit tunnel is greater than the horizontal displacement, which is basically twice of that; (2) The deformation of the left line corresponding to the first excavated area C is 1.4 times greater than that of the right line corresponding to the second excavated area D; (3) The pipe curtain method can effectively reduce the uplift of the existing tunnel in the lower part caused by the excavation of the upper foundation pit, which has reference significance for similar engineering design and construction.

Key words: Excavation Supporting Engineering, Upper Deep Excavation, Regional Transit Tunnel, Numerical Simulation, Deformation