Field Measurement Analysis on Deformation of Adjacent Metro Twin Tunnels Under the Coupling Effect of Servo Supports and Deep Foundation Pit Excavation

To investigate the deformation law of adjacent metro tunnels under the coupling effect of servo supports and deep foundation pit excavation, this study takes an ultra-deep foundation pit adjacent to Hangzhou Metro Line 2 as the research object. A servo support system was adopted for synchronous active loading during excavation, and field monitoring was conducted to analyze the deformation response of existing operating tunnels before and after servo loading. The results indicate that servo loading significantly reduces the rate of increase in tunnel vertical displacement, horizontal displacement, and horizontal relative convergence. It is found that the servo support closest to the tunnel (i.e., the third servo support in the case) exhibits the most prominent control effect—after loading, the vertical displacement rate of the down-line tunnel decreases from −0.04 mm/d to 0 mm/d, and the horizontal displacement rate is reduced by approximately 70%. Moreover, seven days after loading, the horizontal relative convergence rate of the up-line tunnel tends to be 0 mm/d. Servo supports effectively weaken the tunnel’s deformation development during critical stages of ultra-deep foundation pit construction, enabling active and precise control of adjacent operating metro tunnels.