Abstract:There are different points of view about the deformation mechanism of the central pier of the permanent shiplock of the Three Gorges Project. The influences of different excavation sequences on the deformation of the pier are investigated,and parameter sensitivity analysis is made by using FLAC. The numerical results show that the main influential factor for the deformation is the excavation sequence,and the abnormal deformation is caused by asymmetrical excavation sequence at two sides of the pier. It is also found that the existence of the fault F215 cannot result in northward displacement of the south side,and the abnormal inclination cannot occur unless the rock mass of the pier has relatively high stiffness and strength. It may be concluded that the occurrence of the abnormal inclination doesn’t indicate the failure or collapse of the pier. On the contrary,it demonstrates that the pier has high stiffness and behaves elastically. The results provide a theoretical basis for a rational interpretation of the deformation mechanism of the central pier.