Abstract: The deformation characteristics of surrounding rock and the stress of supporting system during the construction of underground powerhouse group on the left bank of Wudongde Hydropower Station in steep stratified strata are analyzed. The deformation and relaxation of surrounding rock caused by rock mass structure and lithological difference are studied by means of in-situ monitoring, geological survey and numerical simulation feedback, with the main powerhouse as the focus, of which analysis of deformation with excavation time and space change law, shallow anchor and deep anchor cable on rock mass structure control effect. The study results show that the displacement of the surrounding rock of the underground powerhouse is 0-40 mm; the larger part of the displacement appears in the middle of the upper wall of the main powerhouse; the B breccia and the small intersection angle position. The larger parts of the excavation are mainly controlled by the rock mass structure and the rock property of B breccia, and the structure is sensitive to the blasting excavation; and the largest displacement of the caverns during the construction period is 65 mm; the displacement of the deep structural plane is the main displacement in this area; and the bolt and anchor cable support has played a good control role. The displacement is mainly in the period of excavation, and is step-growth type in the process of excavation. And the aging characteristics are not obvious; the overall stability of underground powerhouse is better; and the supporting system is in the normal working state.

Key words: underground engineering, construction period, monitoring feedback analysis, deformation characteristics, steeply dipped rock strata, B breccia