FLOW CHARACTERISTICS OF JOINTS UNDER DIFFERENT CONTACT CONDITIONS
XIA Caichu1，2，WANG Wei1，2，3，CAO Shiding1，2，4
(1. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education，Tongji University，Shanghai 200092，China；2. Department of Geotechnical Engineering，Tongji University，Shanghai 200092，China；3. Construction Safety and Quality Supervision Station，Minhang Sub-station，Shanghai 201100，China；4. Shanghai Municipal Engineering Design and Research General Institute，Shanghai 200092，China)
Abstract：Seepage characteristics of rock joints under different contact conditions are studied. Artificial tension rock joints are made of white marble samples taken from construction site of the Yalong River(Jinping II Project)，using cleaving method. Surface topographies of rock joints are measured by a three-dimensional TJXW–3D-typed portable rock surface topography measuring instrument. A self-programmed software is used to calculate parameters for rock joints，including not only 2D fractal dimension of surface topography for each single joint surface，but also 3D fractal dimension of composed topography for vacuum formed by two coupled joint surfaces. Then seepage experiments of the artificial rock joints are carried out. During the experiment，contact condition of rock joints varied by offsetting the relative position of the joints from 1 mm to 6.5 mm. Deficiency of traditional empirical formulas，such as Darcy¢s law，cubic flow law and its modified formula，and seepage formula in turbulent flow，are exposed by comparing experimental results with calculating ones from those traditional empirical formulas. After a thorough study of experimental results，it is discovered that fractal dimensions of single joint surface topography and composed joint topography have great influences on the seepage characteristics of rock joint. By taking permeability and the topography coefficients of rock joint into consideration，a new empirical formula for seepage in rock joints that highly matches the test results is presented，which is much more reasonable in theory and accurate in practice than traditional formulas.
