Abstract:The rock mass fracture is considerably developed in underground caverns of Huanggou Pumped Storage Station,so it is significant for engineering construction to predefine whether there are unstable blocks on excavation planes of underground caverns. According to the engineering geological condition of Huanggou Pumped Storage Station and characteristics of plenty of fractures,the block theory,which is an effective engineering analysis method for the stability of fractured rock mass,is adopted to analyze the stability of surrounding rock of underground caverns. Because there are a lot of fractures in the surrounding rock,computing load of the analysis is very large. Thinking about above-mentioned condition,vector analysis method of block theory is adopted to rapidly analyze block by computer. According to the elements of vector analysis method,combining local three-dimensional coordinate of underground caverns,numerical software MATLAB is adopted to compile calculating program applicable to arched underground cavern. The calculating program needs to input joints occurrence,measuring point coordinate,radius of underground caverns,vertical wall height of underground caverns and other relevant engineering data to search for the existent unstable rock blocks in ranges of underground caverns and to analyze the boundary condition,geometric parameter,failure mode and stability factor of each block in turn. So the vertex three-dimensional coordinates,volume,stability factor and other relevant information of key block can be obtained at last. Then CAD is used to show the position and geometrical shape of key block in three-dimensional space. The information can provide guidance for excavation of underground caverns.