Abstract:The quality of rock mass become unfavorable by the influence of blasting explosion,opening and lag of anchorage and support. The closer the surrounding rock near cave surface is,the worse it becomes. The longer the time after opening without anchorage and support is,the worse it becomes. So it is thought that surrounding rock is heterogeneous,but a parameter-field of space distribution,which is varied with the geological conditions;and opening and support methods are presented. Adopting 3D elastoplastic damage FEM and displacement back-analysis method,the proper parameters of surrounding rocks are determined by sensitivity analysis. Adopting local cross section model,the local parameter-field can be calculated rapidly. Then,the parameter-field of whole 3D model can be built by interpolation. Finally,combined with Pubugou underground powerhouse,the 3D FEM model is built. When monitoring data are inputted,the surrounding rock parameter-field can be obtained. The calculation results are used to predict the displacement and stabilization of surrounding rock. The results show that the distribution of parameters of surrounding rock mechanics calculated agrees well with those measured.