Abstract: In the area of deep sand layer, the deep excavation must be performed at a safe distance from the active subway tunnel structure to ensure the operation safety of the subway. The deformation of the tunnel structure must be strictly controlled. The design, construction and monitoring aspects of the deep excavation have extremely high requirements. Focused on the specific engineering examples, the deformation patterns of the subway tunnel structure at different distances from the deep excavation are studied by using the methods of on-site monitoring and numerical analysis. The results show that the supporting structure with the secant pile wall combined with the concrete internal support meet the deformation control requirements. Moreover, the closer the subway tunnel is to the deep excavation, the greater the horizontal and vertical displacements. Among them, the measured maximum vertical displacement of the subway tunnel roof is 5.65mm, and the maximum horizontal displacement is 4.60 mm. In the design of the deep excavation, the stiffness of the supporting structure should be strengthened locally according to different distances, or the soil improvement on the side of the subway tunnel structure should be performed.

Key words: Deep Excavations, Numerical Simulation, Subway, Deformation Monitoring, Deep Sand Layer