Time-dependent failure of deep-buried marble in Jinping II Hydropower Station

The deep-buried marble in the headrace tunnel of Jinping Ⅱ Hydropower Station exhibit time-dependent failure.The internal mechanism of the phenomenon is comprehensively analyzed by means of tests,monitoring and theoretical analysis.The largest buried depth of the headrace tunnel reaches 2 525m,and the contradiction between the stress and rock mass strength is sharp.The variation of buried depth makes the marble which belongs to brittle rock also exhibit the phenomenon of fracture extension with time.The fracture is regarded as the main excavation response based on the laboratory compression tests.The field anchor stress meters and acoustic wave tests show the time-dependent failure characteristics of deep-buried marble.The parallel-bonded stress corrosion model based on the stress corrosion theory can be employed to satisfactorily simulate such phenomenon.