Abstract: Finite element method（FEM）is adopted to back analyze initial geostress field around the underground power houses of a hydropower station. Three-dimensional elastoplastic finite element analysis is performed for the simulation of excavating of the underground power houses excavations by using hyperbola yield criterion of Zienkiewicz-Pande. In order to reflect the solidification effect on surrounding rock by anchorage and to evaluate rationality of underground openings’ support parameters, a new element mode, which can take the shearing-resistant effect of bolt and the prestressing force of anchorage cable into account, is presented. The finite element calculation result shows that the openings’ layout, construction sequence and support parameters are rational, main openings are stable well.

Key words: back analysis of initial geostress, elastoplastic finite element；stability of surrounding rock；implicit element of bolt and anchorage cable