Research on the fluid flow characteristics of fractal single fractures with different water pressure heads H, fracture widths e and fractal dimension D has been investigated, and a comprehensive index Fr coupling the three factors was proposed. The evolution of flow rate Q, Reynolds number Re, Euler number Eu and equivalent permeability K were discussed. Results suggested that the relationship of Q-e is far away from a cubic form. With increase of H and e, Q showed a growing trend with a power function, Re evolution showed that flow state was changing from laminar flow into a transiting region of laminar-turbulent flow, Eu evolution showed that flow resistance decreased obviously. With increase of e, relationship between Q and hydraulic gradient is evolving from an array distribution to a one-to-one correspondence. With increase of D and H, correlation of K, Re, Eu and Fr usually showed an obvious array distribution.
Seepage characteristics of fractured rocks is a basic scientific problem in energy development fields such as efficient exploitation of oil and gas, safe disposal of nuclear waste and safe operation of hydropower projects. Single fractures are the basic unit of complex fracture structures. And its seepage characteristics are the basis for describing the seepage behaviors of fractured rocks. Cubic law can only approximately describe the seepage law of cracks with no filling, smooth sides and large aperture. When the normal stress of fracture is greater than 10 MPa, the cubic law is no longer applicable (Cook 1992). Romm (1966) believes that the cubic law is applicable when the fracture width is greater than 0.2 mm. Many affecting factors, including stress, fracture shear displacement and normal displacement are important factors affecting single fracture seepage state (Olsson & Barton 2001; Esaki et al. 1999). Zimmerman et al. (1996) and Sisavath et al. (2003) studied the hydraulic characteristics of sinusoidal fracture surface under the effect of normal stress and shear stress, and discussed the applicable conditions of cubic law.
