Abstract:With the construction of a large number of subway shield tunnels, urban tunnels and urban underground utility tunnels, the new tunnels crossing over or below the existing tunnels and the interaction have become one of the key research contents of tunnel engineering. For the existing tunnels, the previous studies have mainly focused on the urban tunnels or shield tunnels. The urban underground utility tunnels have the characteristics of shallow burial depth, small width and thin wall thickness. Therefore, when it is under-passed by a double-line shield tunnel, the internal force and surface settlement of the existing tunnel structure will inevitably be different. Based on the utility tunnel project of Fenhu Station (South Suzhou Railway Station), a three-dimensional finite element model is established by using Midas GTS NX software to analyze the influence of utility tunnel foundation reinforcement on the construction of long-term subway shield tunnel and its interaction. Taking the length of foundation reinforcement and the clear distance between the upper and lower tunnels as the variables, the tunneling pressure of shield machine, the jack thrust and the interface between segments are considered. The study results show that for the project, if the long-term shield tunnel passes through the utility tunnel, the foundation reinforcement of the utility tunnel has no obvious effect on the internal force of the segments. When the double-line shield tunnel passes underneath, the shorter length of foundation reinforcement will increase the axial force (tension) of the existing utility tunnel. For the initial stage of surface settlement, the foundation reinforcement will increase the settlement values of X direction (vertical utility tunnel direction) and Y direction (parallel utility tunnel direction), but significantly reduces the uplift value of the surface after the shield tunnel passes underneath.
