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Abstract A conceptual model of fracture element is presented that characterizes the discrete fracture network with fracture elements. We calculate the equivalent permeability of fracture element based on the principle of equivalence of flux between a single fracture and a square element. But the“stair-case”fracture elements increase the length of flow path，and result in a decrease of flux with an unaltered hydraulic pressure difference. To solve this problem，we modify the fracture elementary permeability through considering the ratio of length of flow path to fracture length；and for the complex fracture network，the isolated fractures，dead-end parts of fractures and the isolated fracture clusters are deleted to build up a connected fracture configuration. To verify the modified equivalent permeability model we perform fluid flow simulations on a series of single fracture，intersecting fractures and complex fracture network. The calculated total flow rate and flux distribution along the downstream outlet are consistent with the analytical results and discrete fracture network model results. The modified equivalent permeability model can also characterize the heterogeneity and anisotropy of fluid flow in fractured rock mass.
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Received: 30 October 2012
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2013, Vol. 32 
