| Rock mass structure of underground powerhouse in Xilongchi Pumped Storage Power Station is mostly low-angled layered rock and unfavourable to successful excavation of the arch, thus systematic monitoring measures were installed in the underground powerhouse. This paper mainly about the stability of surrounding rock in Xilongchi underground powerhouse.After brief introduction of the construction situation and monitoring design, this paper sums up the deformation regulatilies of surrounding rock, the changing rules of deformation with time and heading face; the distribution of plastic zone and regularities of supporting force for anchor bolt and anchor cable based on arranging and analyzing the monitoring datum from multi-spots displacement meters, acoustic-waves-monitors and anchor monitors in the recent 2 yearsAt the same time, the supporting effectiveness and supporting opportunity are studied from the viewpoint of theoretical calculation by using limit equilibrium method and software such as BMP2000 and FLAC3D, with which the excavation and supporting process of the underground powerhouse are numerically simulated.Then the thesis analyzed the characteristics of the stress, deformation and plastic zone of surrounding rock and evaluated the supporting effectiveness by comparing the theoretical calculation results and monitoring datumAt last, the stability of surrounding rock of this project is demonstrated to be reasonable by comparing the monitoring deformation of surrounding rock with several relevant stability criterions used in common at present. Futhermore the paper proposes two methods, namely the speed-ratio method based on deformation speed of rock and absolute-deformation method by synthesizing monitoring datum of several large powerhouse with high sidewalls.
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