Abstract: In order to study the safety of subway tunnels in water-rich sandy strata under the interaction of dynamic load during the construction and operation phases, taking the Nanjing Metro Line 5 passing under the existing Line 1 as the example, this paper establishes a numerical model of the overlapped tunnels to investigate and analyze the subway settlement and the fatigue life under the interaction of the two phases. The results show that: (1) the maximum tunnel settlement during the under-passing construction is 7.5 mm, and the design scheme of micro-disturbed grouting + full-ring steel plate in the tunnel could effectively control the tunnel deformation during this stage; (2) after operation of Line 5, the proportion of settlement at the Line 1 tunnel base in the first year is the largest, accounting for about 65% of the total settlement in the 10-year period, after which the settlement rate gradually converges;(3) through backfilling grouting in new Metro Line 5 it can significantly reduce the long-term operational settlement of Line 1, ensuring the long-term operational safety of Line 1; (4) the fatigue life of the segments at the overlap is the shortest, while the fatigue life of the segments far away from the overlap area is longer, and the overall performance of the project meets the requirements for the design service life of the structure.