In order to study the seepage characteristics of rock mass containing periodic fractures without filling, an analysis model for groundwater flow was built. In this model, two assumption conditions were given for the interface between rock and facture. One condition was that the velocity was equal and the other was that the shear stress was continuous. According to the given conditions, the velocity distribution in fractures was deduced using the Navier−Stokes equation and that in rocks was deduced using the Brinkman-extended Darcy equation. The equivalent permeability coefficient of the theoretic model, i.e. the rock mass containing periodic fractures without filling, was derived from the linear Darcy's law. The derived explicit equation shows that the aperture of fracture plays an important role in the groundwater flow in rock mass. In addition, the laboratory seepage tests were performed to validate this model. During the testing process, concrete and fracture between two pieces of concretes were used to simulate rock and fracture respectively. The average permeability coefficient value measured by tests and the equivalent value calculated from the theoretical expression were in the same order of magnitude, and the error was very small. The test results validate the expression given in this study.
