In numerical calculation and analysis

the inhomogeneity of rock is reflected by giving different and random physical and mechanical parameters without considering the rocks’ structural characters—the contents of mineral composition in the rock. So a new parameter assignment method is provided considering the inhomogeneity of the rock materials—the random parameter assignment method of the rock mineral cell unit. The sort intervals of the minerals cell units are defined based on the sorts and contents of the rock minerals. For each unit

content judgment is dealt with by Monte Carlo mothod; and the corresponding value of the physico- mechanical parameters are given to the cell unit. Then the inhomogeneity of rocks can be described according to the random and uniform assembly of mineral cell units of the model. The method not only takes into account the contents(sorts and ratios)of mineral composition in the rock

but also considers the random distribution characteristic of the mineral. In the light of the random distribution characteristic of the mineral

choosing two minerals and three minerals for parameter assignment respectively; a series of numerical experiments are taken to research the influence of the random distribution characteristic of the mineral on macro mechanical parameters of the model. The study results indicate that the random parameter assignment method of the rock mineral cell unit has dual characteristics of structure and randomness; and the random characteristic is independent of statistical parameter. The randomness has little or no influence on the macro mechanical parameters of the model.