Abstract: The contact area will make flow tortuosity more obvious and influence the flow rate significantly. In order to investigate the effect of contact area on fluid flow through joint, a conceptual flow model is established to obtain the contact influential coefficient. And the influential coefficient is introduced into the equation for flow rate calculation considering the effect of tortuosity; a new equation considering the effect of contact area is derived. As the contact area makes the calculation of tortuosity coefficient more complicated, an algorithm for calculating the average tortuosity coefficient is proposed based on the joint aperture distribution. An artificial marble joint is taken as an object and the surface topography data are scanned. In one hand, flow tests are carried out on the joint specimen under five levels of normal stresses. In the other hand, on the basis of the average tortuosity coefficients and contact area ratios of joint specimen under five levels of normal stresses calculated according to the joint surface topography data, the volumetric flow rates through joint specimen are predicted by the new equation considering contact area presented in this paper and Zimmerman's equation, respectively. Then the predictions of the two equations are compared with experimental observations. It is shown from the comparison results that the predictions of the new equation agree well with experimental observations, while Zimmerman's equation overestimates the flow rate through the joint, thus validating the veracity of the new equation.

Key words: rock mechanics, rough joint, closure deformation, aperture, tortuosity coefficient, contact area