Accurate measurement of aperture distribution plays an important role in evaluating the hydraulic behavior of rock fractures. In this paper, the authors are devoted to the assessment of two methods, proposed by Brown and Wang respectively, for quantitative measurement of fracture aperture distribution. The principles of the two methods are outlined firstly. Three groups of artificial marble fracture specimens are prepared and the surface topography data are obtained by a 3D laser scanning system. Then based on the surface topography data, each method is adopted to calculate the aperture distribution. The mean apertures of fracture specimens are obtained by conducting statistic analysis on the aperture distributions. Constant hydraulic head flow tests on fracture specimens are also performed for inversion calculation of the hydraulic aperture. Comparisons between the mean aperture and hydraulic aperture of fracture specimens are provided to assess the applicability and accuracy of the two methods for quantitative aperture measurement.
The hydraulic behavior of a blocky rock mass is more dependent on the characteristics of the system of fractures within the rock mss than the characteristics of the intact rock, and fractures represent conduits of enhanced hydraulic conductivity relative to the intact rock (Tatone, 2012). Therefore, the analysis of fluid flow through a single rough fracture has become a hot focus in many research areas, such as oil recovery, geothermal energy extraction groundwater flow and the underground disposal of CO2 and radioactive waste. Amongst the various parameters affecting the hydraulic behavior of a fracture, the spatial aperture distribution appears to be very important (Zimmerman & Bodvarsson, 1996), for the spatial aperture distribution affects the tortuosity and connectivity of flow paths, which in turn influence the hydraulic transmissivity of the fracture (Tsang 1984, Berkowitz 2002). In the classical case of laminar fluid flow through a fracture with smooth parallel surfaces, the flow rate is proportional to the cube of the aperture (Snow, 1969). This is the classic cubic law, from which we can draw a conclusion that the aperture plays an important role in fluid flow through a fracture and controls the flowrate to a large extent. Therefore, accurate measurement of aperture distribution is crucial for evaluating the hydraulic behavior of a fracture.