Influence Analysis on Adjacent Tunnel Induced by Foundation Pit Excavation Considering Spatial Effect

The deformation of retaining structures induced by the excavation will cause the change of the earth pressure, which will have an adverse impact on the additional deformation and internal force of adjacent tunnels. Combining the earth pressure with the deformation of the diaphragm wall, a three-dimensional unloading earth pressure calculation model is established considering the spatial effect of excavation. Mindlin’s solution is used to calculate the additional stress at the tunnel axis. The tunnel is regarded as a continuous Euler-Bernoulli beam resting on the Pasternak foundation which considers the continuity of soil deformation, and the response of the tunnel under additional load is obtained. Applying the additional load caused by the excavation to the adjacent tunnel, theoretical method for calculating the additional deformation of tunnels considering spatial effect is obtained. Compared with the history case, the reliability of the method is proved. By applying the method, the influence laws of the maximum deformation of the retaining wall, the distance between the tunnel and the foundation pit and the soil modulus are further analyzed. The research results show that: the increase of the maximum deformation of the diaphragm wall will further increase the deformation and internal force of the tunnel, while the increase of the soil modulus and distance between the tunnel and foundation pit will reduce the additional deformation and internal force of the tunnel.