Line Element Model For Fluid Flow In Three Oimensional Fracture Network And Its Modification

The research on the seepage in fractured rock mass has important significance for the further development of many application disciplines, and it’s also the urgent needs to solve many major practical engineering problems in many engineering field, such as water conservancy and hydropower engineering, civil engineering, petroleum engineering, nuclear engineering and mining of mineral resources, etc. The hydraulic properties of rock mass is mainly controlled by fracture which distributes in rock mass. And in the geological history of the development process, the formation of the shape, orientation and size in rock mass are different, as well as the space combination forms, so that the rock permeability shows anisotropy and heterogeneity. It also determines that the value and hydraulic parameters of rock mass seepage analysis is a research topic which is extremely complex, but very practical. And how to show the heterogeneity is both emphasis and difficulty in this research. In view of this heterogeneity, rock mass seepage model can be classified into three categories:the equivalent continuous fracture network, the discrete fracture network and the mixed model. While the equivalent continuous fracture network has been relatively mature, it’s hard to confirm the size of REV and the equivalent hydraulic parameters. Also it could not describe the special water guiding of the fracture at the same time. The latter two are better in describing the basic law of the seepage in fractured rock mass and reflecting the heterogeneity of rock mass so that they have wide development space. Although the mixed model is better in reflecting the characteristics of the fracture rock mass seepage, it’s difficult to determine water exchange relationship between the structure and the fracture, which limits its use value greatly. That is why this article mainly focuses on the the discrete fracture network which is both according with the objective rule to the most degree and has practical engineering application value.Simulation of3D fracture network seepage in fractured rock mass has very important practical significance for the discrete fracture network. This article based on field measurement of fracture occurrence of statistical regularity, the Monte-Carlo method is used to generate the corresponding fracture network.The graph theory is employed as the mathematical model in depth-first search (DFS) to determine the largest connected component of the fracture network. Based on the intersection relations between fractures, the rock fracture is generalized to a three-dimensional fracture network line element model, whose nodes are the crack disk center and elements are the lines between the centers of the intersected discs. This method will simplify the three-dimensional fracture network seepage model as one-dimensional network, and the seepage calculation amount is greatly reduced. And comparing with the pipe flow model, the equivalent permeability tensor and the flow of both model will be calculated by some examples.