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.

Numerical Simulation of Soil Displacement and Settlement in Deep Foundation Pit Excavations Near Water

“…(1) The current constitutive model cannot accurately reflect the deformation law of all soils in the excavation stage (Chen et al [12], Li et al [16], and Zhang et al [32]). The parameters used in the calculation depended significantly on the geological prospecting data of the project, and the interval between drilling holes was 50~100 m, which cannot accurately describe the stratification change of the excavation surface and surrounding soil.…”

Transverse Force Analysis of Adjacent Shield Tunnel Caused by Foundation Pit Excavation Considering Deformation of Retaining Structures

“…The authors of [20] have considered the collaborative effect of the rotation and dislocation deformation between the segment rings in the study of the longitudinal deformation of the shield tunnel, which can better reflect the characteristics of the longitudinal deformation of the shield tunnel structure. Therefore, the resultant force between the segment rings in the calculation process in this paper can be obtained by that method.…”

“…If the segment ring analyzed is located at y = l, then the horizontal displacement of the tunnel axis at this position is u(l), and the horizontal shear force between the segment ring and adjacent segments of the former and latter rings can be expressed as Q xF (l) and Q xL (l), respectively. From the literature [20], we can obtain…”

“…Furthermore, the unloading model of the foundation pit is far from the actual situation, and the influence of the force between the segment rings of the tunnel on the transverse force is also insufficiently considered. Authors [20] have considered the deformation of the foundation pit' retaining structures and the partition of the region affected in the study of the influence of the foundation pit on the adjacent shield tunnel, which compensates for the deficiencies of the existing foundation pit unloading model. However, it focuses on the longitudinal deformation of shield tunnels, without considering the variety in the tunnel's confining pressure and structural's transverse force.…”

Deformation Response Research of the Existing Subway Tunnel Impacted by Adjacent Foundation Pit Excavation

“…erefore, carrying out a study on the impact of adjacent foundation pit excavation on existing subway tunnels is of great importance for metro safety evaluation. In recent years, many studies on subway tunnel deformation caused by adjacent foundation pit excavation have been carried out, and many results have been obtained [2][3][4][5]; the main research methods are theoretical investigation [6,7] and numerical simulation [8][9][10] using finite element software. ShiI et al [11] verified that the finite element method is a feasible tool to investigate the excavation stages and to study the influences on existing tunnels induced by deep excavations.…”