The study for longitudinal deformation of adjacent shield tunnel due to foundation pit excavation with consideration of the retaining structure deformation

Abstract

By selecting the ratio of the cumulative maximum deformation of the retaining structure to the excavation depth as the control parameter of the retaining structure deformation, this paper established a sidewall unloading model which can consider the deformation of the retaining structure and the spatial effect of foundation pit excavation. Meanwhile, the impact region of the sidewall was divided to calculate the distribution of additional stress caused by foundation pit excavation. On this basis, through introducing the collaborative deformation model for rotation and dislocation of a shield tunnel, this paper studied the longitudinal deformation of the adjacent shield tunnel due to foundation pit excavation. Moreover, several engineering cases were given to verify the reliability of the proposed method, and the influencing factors were analyzed. The following conclusions were obtained: the axial horizontal displacement of the shield tunnel by the side of the foundation pit was normally distributed, and the calculated value was in good agreement with the measured value; the longitudinal deformation of the shield tunnel was mainly induced by the unloading effect of the sidewall of the foundation pit, which was parallel and closed to the tunnel; the soil excavation in the vicinity of the buried depth of the tunnel would result in a significant increase in longitudinal deformation; with the increase in the retaining structure deformation of the foundation pit, the longitudinal deformation of the adjacent shield tunnel and its influence scope also increased; the longitudinal deformation of the shield tunnel decreased with the increase of clearances between the foundation pit and tunnel; and finally, the excavation of the foundation pit had a great influence on the shallowly buried shield tunnel nearby, and the effect of foundation pit excavation on the tunnel decreased with the increase of the burial depth of the shield tunnel. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.