Journal ArticleDOI
Numerical investigation of geometrical and hydraulic properties in a single rock fracture during shear displacement with the Navier–Stokes equations
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In this article, a more detailed 2D numerical model was developed using a laser scanner system with a spacing grid of 0.1mm, and the results of the procedure for shear displacement simulation illustrate the distribution of the absolute velocity and pressure drop under the constant pressure gradient.Abstract:
Extensive research has shown that fluid flow through rock fractures is greatly influenced by surface roughness. For a single rock fracture, the roughness of the upper and bottom surfaces is the same in the initial condition and then its deformation occurs with normal stress and shear stress imposed on the natural rock. Previous researchers have paid considerable attention to describing the roughness of the single fracture and its effects on fluid flow. However, few studies have explained the fluid flow with shear displacement and the direction of the fluid flow velocity field. In this work, a more detailed 2D numerical model was developed using a laser scanner system with a spacing grid of 0.1 mm. To investigate the influence of shear displacement accurately, the COMSOL multiphase codes were applied. By applying the Navier–Stokes equations, the results of the procedure for shear displacement simulation illustrate the distribution of the absolute velocity and pressure drop under the constant pressure gradient. The velocities predicted at the vertical profiles of the inlet were similar to the parabolic velocity curve defined by the cubic laws. The mean mechanical aperture was usually larger than the hydraulic aperture from the measured flow rates, and a devised empirical equation was proposed to describe the relationship between the mechanical aperture and the hydraulic aperture values. The recirculation zones observed in directional fluid flow during shear explain the anisotropy of roughness of a single fracture, and the phenomenon argues the applicability of local cubic laws which overestimate the total fluid flow rate.read more
Citations
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Journal ArticleDOI
Combined Effect of Contact Area, Aperture Variation, and Fracture Connectivity on Fluid Flow through Three-Dimensional Rock Fracture Networks
TL;DR: In this paper , a series of flow simulations were implemented on two types of 3D DFN models constituting fractures having spatially variable apertures and parallel plates, respectively, to investigate the combined effect of contact area, aperture variation, and fracture connectivity on the fluid flow through a fractured medium.
Journal ArticleDOI
Effects of Forward and Reverse Shear Displacements on Geometric and Hydraulic Characteristics of Single Rough Fracture by the Finite Volume Method
TL;DR: In this article , a 2D rough fracture profile was used to establish models of different shear displacements in the forward and reverse directions without contact zone, and the geometric distribution characteristics of the fracture space with shear displacement were analyzed.
Journal ArticleDOI
Research on the Permeability of Water and Sand in the Fractured Rock
TL;DR: In this article , a seepage system was designed and manufactured to test the permeability of water and sand in the fractured rock, and the equations of effective fluidity and non-Darcy factor were obtained by using the genetic algorithm and the fitting parameters were obtained.
Posted ContentDOI
Numerical investigation of fluid flowing through rough fractures subject to shear
TL;DR: In this article , the authors employed numerical simulations to investigate the fluid flow behavior in fractures with different surface roughness under shear, where the shear direction is perpendicular to the flow direction.
Posted ContentDOI
Mesoscopic Study on Seepage Characteristics with Shear Displacement in a Single Fracture
TL;DR: In this paper , the change and distribution of fracture aperture under different shear displacements, especially the measurement of the contact area under shear displacement, is analyzed. And the relationship between volumetric flow rate and pressure gradient during flow field simulation can be well fitted by the Forchheimer equation, and the steepness of the curves is related to the contact areas.
References
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Journal ArticleDOI
Validity of Cubic Law for fluid flow in a deformable rock fracture
TL;DR: The validity of the cubic law for laminar flow of fluids through open fractures consisting of parallel planar plates has been established by others over a wide range of conditions with apertures ranging down to a minimum of 0.2 µm.
VALIDITY OF CUBIC LAW FOR FLUID FLOW IN A DEFORMABLE ROCK FRACTURE - eScholarship
Abstract: The validity of the cubic law for laminar flow of fluids through open fractures consisting of parallel planar plates has been established by others over a wide range of conditions with apertures ranging down to a minimum of 0.2 µm. The law may be given in simplified form by Q/Δh = C(2b)3, where Q is the flow rate, Δh is the difference in hydraulic head, C is a constant that depends on the flow geometry and fluid properties, and 2b is the fracture aperture. The validity of this law for flow in a closed fracture where the surfaces are in contact and the aperture is being decreased under stress has been investigated at room temperature by using homogeneous samples of granite, basalt, and marble. Tension fractures were artificially induced, and the laboratory setup used radial as well as straight flow geometries. Apertures ranged from 250 down to 4µm, which was the minimum size that could be attained under a normal stress of 20 MPa. The cubic law was found to be valid whether the fracture surfaces were held open or were being closed under stress, and the results are not dependent on rock type. Permeability was uniquely defined by fracture aperture and was independent of the stress history used in these investigations. The effects of deviations from the ideal parallel plate concept only cause an apparent reduction in flow and may be incorporated into the cubic law by replacing C by C/ƒ. The factor ƒ varied from 1.04 to 1.65 in these investigations. The model of a fracture that is being closed under normal stress is visualized as being controlled by the strength of the asperities that are in contact. These contact areas are able to withstand significant stresses while maintaining space for fluids to continue to flow as the fracture aperture decreases. The controlling factor is the magnitude of the aperture, and since flow depends on (2b)3, a slight change in aperture evidently can easily dominate any other change in the geometry of the flow field. Thus one does not see any noticeable shift in the correlations of our experimental results in passing from a condition where the fracture surfaces were held open to one where the surfaces were being closed under stress.
Journal ArticleDOI
Hydraulic conductivity of rock fractures
TL;DR: In this article, the authors derived the cubic law of the Navier-Stokes equations for flow between smooth, parallel plates and showed that the effective hydraulic aperture is less than the mean aperture, by a factor that depends on the ratio of the mean value of the aperture to its standard deviation.
Journal ArticleDOI
Fluid flow through rock joints: The effect of surface roughness
TL;DR: In this article, a simulation of flow between rough surfaces was done using a fractal model of surface topography and the hydraulic aperture was compared to the mean separation of the surfaces.
Journal ArticleDOI
Effect of shear displacement on the aperture and permeability of a rock fracture
TL;DR: The results of experiments using radial and unidirectional flow in a carefully described single rough aperture are reported and compared with numerical predictions as discussed by the authors, showing that the aperture distribution became more closely correlated in the direction parallel to the roughness ridges than in the shear direction.