Abstract: Based on the current code defined rock mass classification, a new classification method for a water tunnel excavation by using double shield TBM method is proposed in this paper. The new classification method considers the variation of the excavation parameters in the TBM; gap between the surrounding rock mass and the lining; quantity, shape and size of the excavated materials; [JP2]percentage of the of the structural plane to the machine broke rock fragments; ratio of the soft to hard rock fragments in the excavated materials. This new classification method was used in the Daban Water Diversion Tunnel excavation project.

Key words: Double Shield TBM, Water Diversion Tunnel, Rock Mass Classification