Three-dimensional centrifuge modeling of influence of nearby excavations on existing tunnels and effects of cut-off walls

Centrifuge modeling and numerical simulation are conducted in dry sand to investigate the influence of nearby excavations on the existing tunnels as well as the effectiveness of cut-off walls. The tunnel heaves, internal forces, earth pressures and ground settlements are analyzed as well as the influences of the relative position and excavation depth. As indicated by the tests, the soil heaves at the excavation base are close to the results from the Boussinesq equation. The measured ground settlements are similar to those of the centrifuge modeling by other researchers, while obviously lower than the field measurements. The earth pressures at the excavation side are reduced due to the excavation, while those at the other side increase. The cut-off walls can reduce the ground settlements, change of earth pressures, lateral displacements of diaphragm wall, and uplifts and bending moments of tunnels. The numerical simulation indicates that the tunnel heaves and horizontal displacements decrease as the burial depth of the tunnel and its distance from the diaphragm wall increase, while increases with the increasing excavation depth.