CLASSIFICATION OF FAILURE MODES AND CONTROLLING MEASURES FOR SURROUNDING ROCK OF DEEP TUNNEL IN HARD ROCK

According to the geological conditions,field test,numerical analysis and the entire process of supporting design and construction of tunnels in Jinping II hydropower station,a classification method for failure modes of surrounding rock of deep tunnel in hard rock is established.All of failure phenomena are divided into 3 categories and 9 typical failure modes by the proposed method respectively based on demands of supporting and controlling factors.Furthermore,failure mechanisms and manifestations are analyzed;and controlling measures are provided.Specially,the mechanisms and corresponding controlling measures of rockbursts are discussed.The classification method is applied to identify and analyze various kinds of failure modes,all of which are revealed during excavation of tunnels in Jinping II hydropower station.The recommended controlling measures are adopted referring to the failure modes.The engineering practice indicates that the classification method is comprehensive and practical,which provides an effective way for on-site designers,geologists and constructors to optimize excavation and supporting design of deep tunnel in hard rock.