Abstract: Seepage performance in rock fractures is of the great significance to the safety assessment in the underground engineering. Seepage test through the laboratory prepare on six (6) 3D printed rock fractures samples in accordance with the standard profile curve of the joint roughness coefficient (JRC) with a single opening fracture width of 2.5 mm. The test results show that: (1) when the flow velocity gradually increases, the seepage flow quantity, q, per unit width and the hydraulic gradient, I, presents a strong non-linear relationship. If only the cubic relation is used in the quantity estimation, the hydraulic gradient in the model changes could be significantly underestimated, and therefore, presents an obvious deviation from the estimated value. (2) the JRC has a great influence on the rock fracture seepage. When the inlet flow rate remains unchanged, with the increase of the joint roughness, the pressure on both sides of the rock fracture gradually increases. The non-linearity relationship between the seepage flow quantity, q, per unit width and the hydraulic gradient, I, becomes stronger and stronger.

Key words: rock fractures, joint roughness coefficient, 3d printing, seepage tests