Abstract: Commonly applied methods of classifying the surrounding rock of hydraulic tunnels are based on the construction of shallow buried tunnels and drilling and blasting. Such classifications show poor adaptability to deep buried long hydraulic tunnels constructed with tunnel boring machine (TBM). On the basis of classification methods in China and abroad, we propose a comprehensive classification method which describes not only the surrounding rock stability, and also the types and levels of geological risks for deep buried long hydraulic tunnels constructed with TBM. According to the characteristics of deep buried long hydraulic tunnels and the main geological risks that may be encountered during TBM construction, we select some major assessment factors inclusive of surrounding rock stability, high geostress risk, groundwater risk, as well as excavability. The proposed method is applied to a water conveyance project in Xinjiang and has achieved good result. The research offers technical support for the excavation and support design of deep buried hydraulic tunnel, and also can be regarded as a basis for targeted treatment of possible geological risks during TBM construction.

Key words: deep buried long hydraulic tunnel, TBM, geological investigation, geological risk, engineering rock mass classification