Numerical Investigation of the Influence of Foundation Pit Excavation on the Deformation of Underlying Tunnels Based on a Multi-Factor Orthogonal Test

The excavation of pits will induce the vertical displacement of tunnels and lead to engineering problems. The shape as well as size of a pit, and the complex spatial position relationship between the pit and tunnel will induce different deformation responses of tunnel structures; however, the degree to which each factor influences tunnel structure deformation is still unclear. This paper studied the impact of excavation on the deformation of tunnels via a combination of numerical simulation and orthogonal tests. The deformation of tunnels induced by excavation was studied using a numerical method, after which the sensitivity of influencing factors to tunnel deformation was studied by means of range and variance analyses through a four-factor and three-level orthogonal test. The results show that, for a foundation pit with a long side perpendicular to the tunnel longitude, the excavation has the least influence on tunnel deformation. Tunnel deformation increased with an increase in the excavation depth and decreased with an increase in tunnel–pit vertical and horizontal distance. As the plane shape of the foundation pit is 20 m × 45 m, the depth of excavation is 4 m, the pit tunnel vertical distance is 13 m, and the pit tunnel horizontal distance is 28 m, the tunnel has the least deformation. Based on the results of this study, the position relationship between the pit and the tunnel can be optimized in terms of design and construction, and the aim of controlling tunnel deformation can be achieved.

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