Monitoring result analyses of high slope of five-step ship lock in the Three Gorges Project

The construction of the double-lane five-step ship lock of the Three Gorges Project (TGP) was commenced in 1994, the excavation of the ship lock was completed by the end of 1999, and the ship lock was put in operation in June 2003. The side slopes of the ship lock are characterized by great height (170 m), steepness (70 m in height of upright slope), and great length (over 7000 m in total length). In association with the ship lock, the surrounding rocks in slope have a high potential to deform, with which the magnitude of deformation is restricted. Monitoring results show that the deformation of the five-step ship lock high slopes of the TGP primarily occurred in excavation period, and deformation tended to be stable and convergent during operation period, suggesting the allowable ranges of deformation. At present, the slopes and lock chambers are stable, and the ship lock works well under normal operation condition, enabling the social and economic benefits of the TGP.