Abstract：Back analysis of displacements for the mechanical parameters of an elasto-plastic model for rock mass can be included to an optimization problem. However, before solving the problem，the mechanical parameters influencing the objective function of the problem have to be identified. That is，the mechanical parameters，which can be determined by back-analyzing the displacements in the elasto-plastic model for rock mass，have to be recognized. The Fast Lagrangian Analysis of Continua (FLAC) is used to conduct numerical simulation on displacements around an underground stope. The test design approach on orthogonal table is used to plan the simulation，and the mathematical statistics approach is used to analyze the influence degree of mechanical parameters on displacements in the elasto-plastic model. Approach is established to assess the influence degree of these parameters and identify the parameters which can be determined by back-analyzing the displacements in the elasto-plastic model.
