Abstract: The fracture parallel plate seepage model has been widely applied to describe the processes and characteristics of fluid flow through fractures in rocks, while the actual flow field of the fracture seepage in rocks could be far more complicated than the assumption of rock matrix to be parallel plates. As a result, it draws lots of attentions on investigations on suitability and corrections of the fracture parallel plate seepage model. In this study, by taking the disc fracture model which is closer to the actual fracture shape than the parallel plate model, a physical model of a single disc fracture was constructed in the laboratory. By changing the aperture of the disc fracture in rocks and the sizes of the water inlets and outlets, the seepage experiments under different pressure gradients were conducted to investigate the laws of fluid flow in fractures. The experiment results show that the Forchheimer model fitted the relationship between the seepage flow and pressure gradient inside the disc fracture relatively well while the Darcy law model presents also a good fitting for the Non-Darcy flow regimes. It should be noticed that the calculation formulas of the parameters A and B in the Forchheimer model need to be modified as to the Forchheimer model. Furthermore, an approach has been recommended for those modifications and the corresponding modified calculation formulas with certain reliability have been given based on the experimental results. This study is expected to provide in certain degree theoretical foundations and methods for further investigation of fluid flow through a single fracture in rocks and the complex fracture networks.

Key words: seepage through fractures in rocks, disc fracture model, seepage flow experiment, seepage flow law, model modifications