Abstract: Some key technologies of applying the key block theory in engineering practice are presented to address the stability issue of complex rock blocks involved in the construction of ship lock slope and underground power house of the Three Gorges Project (TGP). Such technologies include the calculation of block volume with any shape, the geometric configuration of a particular type of concave block, and the calculation of water pressure under the general distribution loading condition. By applying these methods to the rock stability analysis and reinforcement evaluation in the shiplock slopes and the underground powerhouse of TGP, key blocks can be identified under the condition of cutting of complex rock mass geological discontinuities, and the stability of key blocks under various load combinations can be evaluated. Applications to the geometric configuration and stability analysis of hundreds of blocks in the construction period of the ship lock slope excavation of TGP demonstrate that the results of stability analysis are roughly consistent with the actual characteristics of exposed blocks and their stability state on site. In conclusion, the methods of rock mass stability analysis based on key block theory proposed in this paper are of good pertinence and practicability, and offer theoretical basis for the rock stability analysis of other projects.

Key words: Three Gorges Project, ship lock slope, rock mass structure, key block theory, stability analysis, engineering application