Studies On Discrete Fracture Network Modeling Based On Monte-Carlo And Permeability Tensor Of Rock Masses

The fractured rock mass naturally has several knids of fractures. The mechanical characteristics of fractured rock mass such as strength, deformability and permeability influences the design, construction, operation and maintenance of rock engineering. At present, the ordinary mechanical and seepage behivors of the fractured rock mass have been systemically studied. But limited literatures have been found in the permeability rules and actual application research on speepage of the the rock mass. The discrete fracture network model is suitable to simulate the seepage in a rock mass, where fracture distribution follows a certain statistical function and the groundwater seepage is mainly controled by fractures. In this research the discrete fracture network model is established by using Monte-Carlo meathod in MATLAB. The calculation methods are given for the discrete fracture network model in different boundary conditions. The effects of the influencing factors on seepage of the rock mass are studied.(1) Based on detailed analysis for the random distribution laws for every single geometrical property for rock fracture, the computational programs in MATLAB have been coded for 2-D discrete fracture network model by using Moute-Carlo method to simulate the discrete fracture network model. Futthor more, the discrete fracture network model is established.(2) The mathematical expression is deduced for calculating the permeability coefficient for 2-D steady-state flow for two kinds of hydraulic boundary conditions. The computational program is coded for the two kinds of hydraulic boundary conditions in MATLAB by utilzing the powerful ability in matrix computation. After detailed verificaion studies, the basic frature network model has been validated.(3) According to the calculation theory for the permeability tensor, the computaional method has been developed to fit the permeability coefficients for every hydraulic direction for 2-D fracture network system into a permeability ellipse. And the corresponding computatioal program is coded in MATLAB.(4) Finally, by using the method for the discrete fracture network model established in this resrerch and the MATLAB programs for calculating of the permeability coefficient in different hydraulic boundary conditions, the effects of every single influencing factors on permeability of a fractured rock mass have been studied. The parametric studies have been performed on the geometrical properties for a rock fracture: fracture orientation, fracture spacing or density, trace length and aperture. It has been conclude that all these influencing geometrical properties have influences on the permeability of a rock mass. The aperture bewteen the adjacent fractures has the maximum impact on the permeabilty of the rock mass, while the trace length of the fracture has the smallest influences on the permeability of the rock mass. It has been also found that the influences of the fracture orientaion on the permeability of a rock mass has obivioues directional effect.