There are large numbers of holes and cracks existed in the natural rock mass

these defects not only change the mechanical character of rock mass

but also affect the seepage characteristics of rock mass. Based on analyzing the present production of seepage characteristics of fractured rock mass

the mechanical character of a rock mass with a single joint and the mechanical function that the seepage impacted on rock mass with a single joint are discussed; and the relation between the permeability coefficient and 3D stresses in the rock mass with a single joint is studied. The influence of the crack coarseness degree on the seepage and the different influences of the different acting directions of stresses on the seepage characteristics of rock mass are considered; the seepage characteristics of rock masses with a single joint under 3D stresses is analyzed; and the relation between stresses acted on the crack and the permeability coefficient is proposed. It is shown that the vertical stress acted on the face of the crack takes a dominant effect on the permeability of rock mass; and the permeability coefficient decreases rapidly with the increasing of the vertical stress acted on the face of the crack. By analyzing and comparing the result of an experiment of seepage law made by Zhao Yang-sheng

the correctness of the expression of permeability coefficient of fractured rock mass with a single joint proposed in this paper

is proved.