Document Type : Article
Authors
1
Department of Mining EngineeringCortain University, Australia
2
Dept. of Mining and Metallurgical Engineering Amirkabir University of Technology
Abstract
This paper presents the fundamentals of groundwater modeling in fractured media and also the technical details of a desirable modeling method in discontinuous rocks. In this paper, the modeling of fluid flow in rock mass is studied using the distinct fracture network (DFN) concept. A new computational code, FNETF, has been developed for generating DFN and fluid flow analysis. The FNETF computational code uses a Monte Carlo approach to generate two-dimensional discrete fracture networks, based on the statistics of the geometrical characteristics of the fracture, in terms of location in the generated region, orientation with respect to the coordinate axes, length, and aperture. In this case, individual realizations of hydraulic attribute distribution, which are formed by discrete fractures, re enerated from a set of probability distributions describing the geometry of the fractures. Because the generated fractures are finite, a relatively large number of fractures in the network may not be perfectly connected and some do not ontribute to the flow process. These hydraulically inactive fractures should be removed from the domain and can be recognized as isolated sub-networks, singly connected fractures, and dead end fractures, which have not omplete nterconnection between other percolating fractures or flow domain boundaries. Once a fracture network is egularized, a finite element mesh is generated for the percolating graphs, consisting of nodes and elements that are fracture ntersections and fracture segments between nodes, respectively. The hydraulic head at each node and steady state flow rate in each element are calculated using a flow network technique, based on the mass continuity equations and cubic law. The validity of the developed computational code is explored by predicting the groundwater inflow to the powerhouse cavern of the Siahbisheh pump storage project in the North of Iran. The main input data forfluid flow odeling hrough a fracture network were captured from ite nvestigation, etailed easurements f roundwater level, and eometrical characteristics of fracture. A flow domain, 122m wide and 129.75m high, was used to simulate water inflow into the Siahbisheh powerhouse cavern. The simulation of water inflow into the powerhouse cavern for 0+071 to 0+085 chainages was done using the FNETF computational code and field data. Based on direct aperture back calibration, he equivalent hydraulic aperture is considered to be 0.452mm. Comparison of results indicates that there is ppropriate correspondence between inflow simulations through the DFN model and those measured. Therefore, DFN models can be utilized for fluid flow analysis in the near-field domains in discontinuous media, showing the appropriate results of rock mass hydraulic modeling.
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