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Abstract Uneven distribution of joint apertures mainly causes the tortuosity of flow through a rough joint. Taking two joint specimens B01 and B02 as research objects，laboratory flow tests and numerical simulations through the specimens are performed after scanning three-dimensional(3D) surface topography of joint. The tortuous streamlines of flow through a joint are derived from numerical simulations；and the tortuosity coefficient which quantitatively describes the tortuosity effect of flow through a joint is defined and calculated according to the 3D void composite topography. Then based on modified cubic law taking into account the roughness of joint surface，the new equation accounting for tortuosity effect for calculating flow volumetric rate through a joint is deduced by applying the equivalent channel model which is adopted to analyze the permeability of rock. The two constants A and B in the new equation are obtained by fitting the numerical simulation results of joint specimen B01. Then the flow rates of joint specimen B02 derived from the new equation and numerical simulations are compared with each other to validate the new equation. Furthermore，the flow volumetric rates of the two joint specimens derived from the new equation，SU Baoyu empirical method and laboratory flow experiments are compared with each other，which shows that the results obtained by the new equation agree well with experimental observations，while the SU Baoyu empirical method overestimates the flow rates，thus verifying the validity of the new equation.
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Received: 14 July 2011
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2011, Vol. 30 
