Modelling method of heterogeneous rock mass and DEM investigation of seepage characteristics

The Weibull distribution is used to describe the heterogeneity of rock hydraulics and embedded into the Fish program which is based on the discrete element method. The developed program overcomes the limitation of the Universal Distinct Element Code (UDEC) software regarding the number of parameter groups, which cannot exceed 50. A method for parameter assignment of heterogeneous rocks is proposed together with a method for estimating the initial flow rate value of heterogeneous models. Based on the established heterogeneity calculation model, the influence of block homogeneity, hydraulic aperture homogeneity, and stress on the seepage characteristics is studied. The results indicate that under zero stress conditions, the flow rate is positively correlated with N0.5 showing a strong linear relationship. The linear relationship is gradually enhanced with the increase in the shape parameters. The relationship between the flow rate and shape parameters is logarithmic with a correlation coefficient greater than 0.9654. The relationship between the flow rate and the axial pressure and confining pressure can be described by quadratic and cubic polynomials, respectively, based on which we further discuss the variation characteristics of equivalent hydraulic apertures under the various axial pressures, confining pressures, and shape parameters. A method for the interaction between MATLAB and UDEC data is proposed, which can realize the construction and parameter assignment of heterogeneous models, This program also breaks through the limitation that the number of parameters in UDEC can not exceed 50.A method for estimating the initial total flow value Q of a heterogeneous model is proposed.The seepage characteristics of heterogeneous rocks and the relationship between flow rate and axial pressure and confining pressure are analyzed under different stress environments.