Abstract: The surrounding rock quality of underground cavern is reduced because of structural planes. Due to this, the mechanical parameters of surrounding rocks of different classifications are difficult to be decided accurately by in-door tests. A novel method of estimating mechanical parameters by analytical decomposition model is proposed. The model is established by constructing 3-D structural plane network models for different rocks using FracSim 3D program based on the results of surrounding rock classification. The anisotropy of rockmass characteristics is reflected by intercepting the 2-D structural plane network in X, Y, Z coordinates. In subsequence, the mechanical parameters of intact blocks and related structural planes are obtained as the basic input parameters of the model. Finally, Phase 2D program is adopted to establish the numerical model of rockmass structure, and the numerical simulation of uniaxial compression and triaxial compression tests by effective control of boundary conditions is carried out to predict the rock strength and deformation characteristics in macro-equivalent model, hence obtaining the mechanical parameters of surrounding rock.

Key words: rock mechanics, analytical decomposition model, three-dimensional structural plane network model, numerical simulation, mechanical parameters, FracSim 3D, Phase 2D