Simulations of tunnel excavation in 2D and 3D conditions considering building loads

Two-dimensional model tests of group pile and piled raft using trap door apparatus are carried out to investigate the effects of the building loads during tunnel excavation. 2D and 3D finite element analyses using elastoplastic subloading tij model are also conducted in this research. The deformation mechanism and the earth pressure distribution during the tunnel excavation in the ground by the building loads are different from those of the green field situation. Surface settlement trough for tunnel excavation in the ground disturbed by existing buildings does not follow the usual pattern of a Gaussian distribution curve, as generally observed for the green field condition. Due to the building loads, unsymmetrical earth pressure distribution is seen at the level of tunnel, even after completion of tunnel excavation. The settlements of the pile cap are unequal for sequential excavation in 3D condition. The numerical results show very good agreement with the results of the model tests.