Abstract：This paper examines the newly built Nijiaqiao Station transfer channel of the Chengdu Metro Line 8 undercrossing the existing Line 1 station at zero distance. The influence range of the existing Line 1 station under the condition of underpass zero-distance tunneling is studied via numerical simulations and on-site monitoring. The main conclusions are as follows. ①The settlement index of the floor of the existing station, as affected by the construction process of the underpass sequence excavation, indicates that the settlement trough is not symmetric. The influence range and the settlement values increase with increasing excavation area. ②The axial strain increment index of the columns in the existing station indicate that the column closest to the excavation pilot tunnel has the largest strain increment, which it is a tensile strain increment, i.e, the compressive strain decreases. Overall, columns with greater distances from the tunnel have smaller strain increments, all of which present compressive strain increments. The strain increments of the columns in lower floors are generally larger than those in upper floors. ③The influence range of the existing station caused by the underpass tunneling increases with the excavation area. The final influence range of the existing subway station under the condition of underpass zero-distance tunneling is approximately 49 m, that is, it extends outward from the left and right boundaries of the newly built channel by approximately 13 m. These findings can be used as a reference for similar projects in the future.
