ANALYSES OF SECURITY MONITORING AND SURROUNDING ROCK STABILITY FOR DIVERSION TUNNEL IN CONSTRUCTION OF YANGFANGGOU HYDROPOWER PROJECT

Two diversion tunnels are arranged on the right bank of Yangfanggou Hydropower Project, it sets a total of thirteen permanent monitoring cross section in construction period, according to the amount of monitoring date and results from the multi-point extensometer, anchor stress and tendon dynameter Installed, it shows that the deformation of diversion tunnels occurs mainly in the left wall, Lower excavation has a big influence to the stability of tunnels, the effect of blasting on the side wall is larger than that on the top arch.the surrounding rock about metamorphic siltstone and the turning segment of both sides walls have the phenomenon of stress adjustment, but the surrounding rock is stable on the whole. Security monitoring better guide the construction management, to escort for the smooth construction project, but also provides valuable experience for similar engineering construction in the future.