Combined effect of tortuosity and surface roughness on estimation of flow rate through a single rough joint

Abstract

Fluid flow through rock joints is greatly influenced by tortuosity and surface roughness, which cause a deviation from the cubic law of joint permeability. In this paper, in order to consider the combined effects of tortuosity and surface roughness on flow rate through a rough joint, a semi-empirical equation is first presented. In this equation, the impacts of tortuosity and surface roughness are represented by three quantitative parameters i.e., the tortuosity τ, surface tortuosity coefficient T s and relative roughness Δ/2d, all of which can be computed based on surface topography data. Furthermore, the empirical constant A in the equation is determined according to the results of flow tests on three artificial joint specimens. Then the validity of the semi-empirical equation is confirmed by use of previously published experimental and numerical results. The obtained semi-empirical equation can predict the fluid flow rates through a rough joint well, and will be helpful to investigate the permeability of rock masses. © 2013 Sinopec Geophysical Research Institute.