Experimental and Numerical Investigation on the Effects of Foundation Pit Excavation on Adjacent Tunnels in Soft Soil

Excavations near an existing tunnel are often encountered in underground construction. The influence of the excavation on the adjacent tunnels is not yet fully understood. This study presented a centrifugal model test about excavation next to existing tunnels in soft soil foundation. The bending moment of diaphragm wall, surface settlement, tunnel deformation, and earth pressure around the tunnel were mainly studied. The influence of tunnel location is further studied by numerical simulation. During the stabilization stage of foundation pit, the diaphragm walls present convex deformation towards foundation pit, and the surface settlement outside the diaphragm wall appears to be the concave groove type. During the overexcavation stage, the diaphragm walls are almost damaged, and the shear bands are nearly tangent to the tunnels. The displacement of the tunnels and the surface settlement rapidly increase. The deformation of the diaphragm wall and the surface settlement are limited by the existing tunnel. The numerical results indicate that the change of tunnel location has little effect on the retaining wall but an obvious effect on the tunnel itself.