Abstract: Prestressed anchor cable is the main engineering measure for stability control of surrounding rock mass in large underground caverns. Aiming at the problem of unloading stability of rock mass excavation and long-term bearing safety of anchor support system in high-stress area, the long-term in-situ monitoring results of systematic anchor cable are deeply analysed. In this paper, we investigate the stress characteristics and space-time variation of the anchor cable, and the time-dependent characteristics of the pre-stress of anchor cable in the underground powerhouse system of Jinping I hydropower station located in Southwest of China. The factors influencing the long-term safety of high bearing anchorage cable structure are discussed, and the long-term safety of anchoring system is evaluated with the numerical simulation method. The obtained results show obviously different from them in the conventional cavern. Most of the anchor cables for supporting deep rock mass of this underground cavern exceed the designed locking value, the load of the cable system is high, the continuous growth time becomes long, and the time effect characteristics is greatly significant. The main factors affecting the long-term bearing capacity of anchor cable include the creep of rock mass, initial tension stress of anchor cable, uneven stress of anchor cable. The analysis indicates that the anchorage cable long-term bearing safety is guaranteed.

Key words: anchor cable in-situ monitoring, aging characteristics, high geo-stress, Jinping I hydropower station, underground powerhouse, long-term risk analysis