Abstract: The fluid movement in rock mass is extremely complicated due to the existence of a large number of rough and irregular fractures. To address the difficulties such as concealment and non-repeatability of physical model in natural rough rock fissure seepage tests, a fissure channel with rough joint surface was constructed based on a three-dimensional Weierstrass-Mandelbrot fractal function. Using 3D printing technique, a transparent and refined fracture channel model was obtained, and the fracture seepage diffusion movements under different conditions were studied by using microfluidic control instruments. The relationships between the discharge of fracture channel and the pressure head, the fracture width and the fractal dimension were analyzed. The results show that in fractal fractures, the discharge of fracture channel is linear with the pressure head; the single-wide discharge is approximately cubic with the width of the fracture channel, which is similar to the parallel plate cubic law. Considering the influence of fractal dimension, the discharge through the fracture channel increases with the increase of fractal dimension. The cubic law of seepage in rough fractures can be modified by the power exponent function related to the fractal dimension.

Key words: rock fissure, seepage, fractal dimension, roughness, laboratory test, 3D printing, cubic law